5 - Cell Signaling (Part 2) Flashcards
transmembrane proteins with their ligand-binding domain on the outer surface of the plasma membrane
enzyme-coupled receptors
has intrinsic enzyme activity or associates directly with enzyme
cytosolic domain
each subunit of an enzyme-coupled receptor has typically how many transmembrane segments
one transmembrane segments
- most common class of signaling by enzyme-coupled receptors
- where many extracellular signal proteins act through
receptor tyrosine kinase (RTKs)
How many human RTKs are classified into 20
structural subfamilies
60 human RTKs
each 20 structural subfamilies are dedicated to its complementary family of ____ ____
protein ligands
the binding of the signal protein to
the ligand-binding domain on the
extracellular side of the receptor
activates the _____ _____ ____ on the cytosolic side?
tyrosine kinase domain
the binding of the ___ protein to
the ___-binding domain on the
extracellular side of the receptor
activates the tyrosine kinase
domain on the cytosolic side
signal
ligand
activation of the tyrosine kinase
domain on the cytosolic side leads to?
phosphorylation of tyrosine side chains on the cytosolic part of the receptor
phosphorylation of tyrosine side chains creates what
phosphotyrosine docking sites
phosphorylation โ ___________
docking sites
phosphotyrosine
ligand binding causes the receptors to ?
dimerize
causes the receptors to dimerize
ligand binding
ligand binding causes the receptors to
dimerize, bringing the two cytoplasmic
_____ _____together and thereby
promoting their activation โ
_________
kinase domains
phosphorylation
dimerization brings the kinase domains close to each other in an orientation that allows them to phosphorylate each other on specific tyrosines
insulin receptor
phosphorylation of the kinase domains promote?
conformational changes that fully activate both kinase domains
the kinase is not activated by phosphorylation but by conformational changes brought about by interactions between the two kinase domains outside their active sites
epidermal growth factor (EGF),
Once the kinase domains of an RTK dimer are activated, they phosphorylate?
multiple additional sites in the cytosolic parts of the receptor
phosphorylation of multiple additional sites in the cytosolic parts of the receptor creates high-affinity ____ ___ for intracellular signaling proteins
docking sites
signaling proteins binds to a particular __________ site on the activated receptors
phosphorylated
why signaling proteins binds to a particular phosphorylated site on the activated receptors
it contains a specific phosphotyrosine-binding domain that recognizes surrounding features of the polypeptide chain in addition to the phosphotyrosine.
Once bound to the activated RTK, a signaling protein may become what?
phosphorylated on
tyrosines and become activated
serves as a switch to trigger the assembly of an intracellular signaling complex
receptor phosphorylation
families of monomeric GTPases
Ras superfamily
relay signals from cell-surface receptors
Ras families
can coordinately spread the signal along several distinct downstream
signaling pathways, thereby acting as a signaling hub.
Ras or Rho family member
can coordinately spread the
signal along several distinct
downstream signaling
pathways
signaling hub
three major, closely related Ras proteins in humans
H-
K-
N-Ras
contains one or more covalently attached lipid
groups
Ras proteins
required when RTKs signal to the nucleus to stimulate cell proliferation or
differentiation
Ras protein
Ras protein is required when RTKs signal to the nucleus to stimulate?
cell proliferation or
differentiation
cell proliferation or differentiation require changes in?
gene expression
express hyperactive mutant forms of Ras
30% of human tumors
Ras functions as a _______ ____ , cycling
between two distinct conformational states
molecular switch
regulate Ras activity by influencing its
transition between active and inactive
states
two classes of signaling proteins
two classes of signaling proteins regulate Ras activity by influencing its
transition between?
active and inactive
states
stimulate the dissociation of GDP and the subsequent uptake of GTP from the cytosol, thereby activating Ras
Ras guanine nucleotide exchange
factors (Ras-GEFs)
Ras guanine nucleotide exchange
factors (Ras-GEFs) stimulate the dissociation of ___ and the subsequent uptake of ___ from the cytosol, thereby activating ___
GDP
GTP
Ras
increase the rate of hydrolysis of
bound GTP by Ras, thereby inactivating Ras
Ras GTPase-activating proteins (Ras-GAPs)
Ras GTPase-activating proteins (Ras-GAPs) inactivate ___
Ras
resistant to GAP-mediated GTPase stimulation
Hyperactive mutant forms of Ras
Hyperactive mutant forms of Ras are
resistant to ___-______ ______
GAP-mediated GTPase
how do RTKs normally activate Ras?
either activate a Ras-GEF or inhibit a
Ras-GAP
has a similar effect to the loss of function of Ras itself
loss of function of a Ras-GEF
GEF that mediates Ras activation by RTKs was discovered by genetic studies of eye development in Drosophila, where an RTK called _______ is required for the formation of a photoreceptor cell called R7
Sevenless (Sev)
Sevenless (Sev) is required for the formation of a photoreceptor cell called?
R7
Genetic screens for components of this signaling pathway led to the discovery of a Ras-GEF called
Son-of-sevenless (Sos)
an adaptor protein that links the Sev receptor to the Sos protein
Grb2
Grb2 links the ___
receptor to the ___ protein
Sev to Sos
promotes Ras activation
Sos
Once activated, it activates various other signaling proteins to relay the signal downstream
Ras
usually short-lived
tyrosine phosphorylations and the activation of Ras
quickly reverse the phosphorylations
tyrosine-specific protein phosphatases
induce activated Ras to inactivate itself by hydrolyzing its bound GTP to GDP
Ras-GAPS
To stimulate cells to
proliferate or differentiate, these short-lived signaling events must be converted
into longer-lasting ones
tyrosine-specific protein phosphatases
and Ras-GAPS
three components of this system form a functional signaling module that has been remarkably well conserved
during evolution and is used, with variations, in many different signaling contexts
mitogen-activated protein kinase
module (MAP kinase module)
MAP kinase module three components
MAPK (Erk)
MAPKK (Mek)
MAPKKK (Raf)
relays the signal
downstream by phosphorylation
MAP kinase
enters the nucleus and phosphorylates one or more components of a transcription regulatory complex
Erk
Erk enters the _____
nucleus
phosphorylation of one or more components of a transcription regulatory complex by Erk activates the what?
immediate early genes
(transcription regulators)
conveys signals from the cell surface to the nucleus and alters
the pattern of gene expression
Ras-MAP-kinase signaling pathways
Ras-MAP-kinase signaling pathways convey signals from the cell ____ to _____ ?
cell surface to
the nucleus
Ras-MAP-kinase signaling pathways alters the pattern of
gene expression
mediates
different responses in the same cell
MAP kinase modules
help prevent crosstalk between parallel MAP kinase modules
scaffold proteins
How many MAP kinase modules can
operate in a mammalian cell
five parallel MAP kinase modules
five parallel MAP kinase module make use of at least how many MAP kinases, MAPKKs, and
MAPKKK
12 MAP kinases
7 MAPKKs
7 MAPKKK
activated by different kinds of cell stresses, such as ultraviolet (UV), heat shock, and osmotic stress
JNK and p38
reduces the opportunities for amplification and spreading of the signal to different
parts of the cell
scaffold strategy
regulate both the actin and microtubule cytoskeletons, controlling cell shape, polarity, motility, and adhesion
Rho family monomeric GTPases
What do Rho family monomeric GTPases regulate?
both the actin and microtubules cytoskeleton
regulation of both the actin and
microtubules cytoskeleton controll what?
cell shape, polarity, motility, and
adhesion
Rho family monomeric GTPases also regulate?
cell-cycle progression
gene transcription
membrane transport
Rho family monomeric GTPases play a key part in the guidance of cell ______ and ____ ___ _______?
cell migration and nerve axon outgrowth
three best-characterized Rho family members
Rho
Rac
Cdc42
activates Rho family
GEFS
inactivates Rho family
GAPs
often bound to guanine nucleotide dissociation inhibitors (GDIs) in the cytosol
inactive Rho family GTPases
inactive Rho family GTPases often bound to?
guanine nucleotide dissociation inhibitors (GDIs)
provides an example of how RTKs can activate a Rho GTPase.
ephrin family
Ephrins bind and thereby activate members of the?
Eph family of RTKs
found on the surface of motor neurons and helps guide the migrating tip of the axon (called a growth cone) to its muscle target
Eph family
One member of the Eph family is found where
surface of motor neurons
migrating tip of the axon is also known as
growth cone
activates the Eph receptor
binding of a cell-surface ephrin
protein
What does binding of a cell-surface ephrin
protein activates
Eph receptor
activation of the Eph receptor cause growth cones to ____
collapse
growth cone collapse; ____ them
from inappropriate regions and
keeping them on track
repelling
activate RhoA (Rhoa-GTP)
Rho-GEF ephexin
It is where major changes in the behavior of a cell tend to depend
change in gene expression
carry out their effects by initiating signaling pathways that change the activities of transcription regulators
extracellular signaling molecules
extracellular signaling moleculescarry out their effects by initiating signaling pathways that change the activities of ?
transcription regulators
controlled in gene expression
less common signaling mechanisms
pathways that depend on regulated ________
proteolysis
do not employ cell-surface receptors but enter the cell and interact directly with transcription regulators to perform their functions
class of extracellular signal molecules
-the daily cycle of light and dark
circadian rhythm
gene expression controlled by _____ rhythm
circadian
- used wildly in animal development
- has a general role in controlling cell fate
choices and regulating pattern formation and continual renewal of tissues
Notch receptor protein
General roles of Notch receptor protein
- controlling cell face choices
- regulating pattern formation
- continual renewal of tissues
Notch receptor protein is best known for production of?
Drosophila neural cells
when a precursor cell commits to becoming a ____ cell โ signal to its _______ ______ not to do the same
neural
immediate neighbors
commits to becoming a neural cell
precursor cell
contact-dependent signaling mechanism that is activated by a single-pass transmembrane signal protein called Delta
lateral inhibition
lateral inhibition is activated by signal protein called?
Delta
Delta binds to?
Notch receptor protein
- a single-pass transmembrane protein that requires proteolytic processing to function.
- It acts as a latent transcription regulator
Notch proteins
Notch proteins require ______ ________ to function
proteolytic processing
Notch proteins act as?
latent transcription regulator
binding of ____ โ plasma-membrane-bound ______ cleaves off the cytoplasmic tail of Notch โ tail translocates into the nucleus to
activated the transcription of ___
response genes
Delta
protease
Notch
cleaves off the cytoplasmic tail of Notch
a plasma-membrane-bound protease
translocates into the nucleus to activate the transcription of a set of Notch response genes
released tail
acts by binding to a DNA-binding protein, converting it from a transcriptional repressor into a transcriptional activator
Notch tail fragment
Notch tail fragment convert DNA-binding protein from transcriptional ____ into a transcriptional ______
transcriptional repressor into a transcriptional activator
undergoes three successive proteolytic cleavage steps
Notch receptor
Notch receptor undergoes three
successive _______ _____ steps
proteolytic cleavage steps
how many successive proteolytic cleavage steps does the notch receptor undergo?
3
In three successive proteolytic cleavage steps of notch receptors, only ___ depend on Delta binding
2
two out of the three successive proteolytic cleavage steps of notch receptor depend on?
Delta binding
1st proteolytic cleavage
normal biosynthesis
2nd proteolytic cleavage
binding of Delta to Notch
3rd proteolytic cleavage
cutting free the cytoplasmic tail of
the activated receptor
- cutting free the cytoplasmic tail of the activated receptor
final cleavage of the Notch tail
final cleavage of the Notch tail occurs just within the transmembrane segment, and it is mediated by a protease complex called
ฮณ-secretase
are secreted signal molecules that act as local mediators and morphogens
Wnt proteins
Wnt proteins act as?
local mediators and morphogens
Wnt proteins were discovered in?
flies and in mice
originally came to light because of its role as a morphogen in wing development
Drosophila, the Wingless (Wg) gene
was found because it promoted
the development of breast tumors when activated by the integration of a virus next
to it
In mice, the Int1 gene
activate at least two types of intracellular signaling pathways
Wnts
centered on the latent transcription regulator ฮฒ-catenin
Wnt/ฮฒ-catenin pathway
Wnt/ฮฒ-catenin pathway is centered on the latent transcription regulator _-_____
ฮฒ-catenin
coordinates the polarization of cells in the plane of a developing epithelium
planar polarity pathway
acts by regulating the proteolysis of the multifunctional protein ฮฒ-catenin
Wnt/ฮฒ-catenin pathway
located at cellโcell junctions and thereby contributes to the control of cellโcell adhesion
portion of the cellโs ฮฒ-catenin
Degradation depends on a large protein _______ _____
degradation complex
degradation complex binds _-____ and keeps it out of the nucleus while promoting its degradation
ฮฒ-catenin
binds to ฮฒ-catenin and keeps it out of the
nucleus while promoting its degradation
degradation complex
four other proteins of degradation complex
- casein kinase 1 (CK1)
- glycogen synthase kinase 3 (GSK3)
- axin
- Adenomatous polyposis coli (APC)
phosphorylates the ฮฒ-catenin
casein kinase 1 (CK1) and glycogen synthase kinase 3 (GSK3)
hold the protein complex together
axin and Adenomatous polyposis coli (APC)
How does Wnt protein regulate ฮฒ-catenin proteolysis
by binding to both a Frizzled protein and a co-receptor related to LDL receptor (LDL-receptor-related protein LRP)
What does activated receptor complex recruit
Dishevelled scaffold proteins
What does activated receptor complex promote
phosphorylation of the LRP receptor by GSK3 and CK1
brought to the receptor complex and inactivated, thereby disrupting the ฮฒ-catenin degradation complex
Axin
Disrupted when axin is inactive
ฮฒ-catenin degradation complex
When the phosphorylation and degradation of ฮฒ-catenin are prevented, it alters the pattern of ____ _______
gene transcription
Wnt-responsive genes are kept silent by an
inhibitory complex
no Wnt signaling
bound to a co-repressor protein of the Groucho family
LEF1/TCF family
LEF1/TCF family is bound to?
co-repressor protein of the Groucho
family
ฮฒ-catenin functions as a coactivator, inducing the transcription of the Wnt target genes
with Wnt signal
With Wnt signal, its transcription is induced when ฮฒ-catenin functions as a coactivator
transcription of the Wnt target genes
switch from transcriptional repression to transcriptional activation
Wnt/ฮฒ-catenin signaling
important regulator of cell growth and prolifereation
Myc
occure in 80% of human colon cancers
mutation in Apc gene
inhibit the proteinโs ability to bind ฮฒ-catenin, so that ฮฒ-catenin accumulates in the nucleus and stimulates the transcription of c-Myc
and other Wnt target genes
mutation in Apc gene
mutation in Apc gene inhibit the proteinโs ability to bind _-_____
ฮฒ-catenin
When ฮฒ-catenin accumulates in the nucleus and stimulates the transcription of _-___
and other ___ target genes
c-Myc
Wnt
- secreted signal molecules and act as local mediators and morphogens
- activate latent transcription
regulators by inhibiting their degradation
hedgehog proteins
hedgehog proteins activate this transcription
regulators by inhibiting their degradation
latent transcription regulators
hedgehog proteins trigger a switch from transcriptional ____ to transcriptional ____, and excessive signaling along either
pathway in adult cells can lead to
____
repression
activation
cancer
were discovered in Drosophila
Hedgehog proteins
Mutation of the Hedgehog gene produces a ____ covered with ____ _____, like a hedgehog
larva
spiky processes (denticles)
three genes that encode Hedgehog proteins in vertebrates
Sonic, Desert, and Indian hedgehog
Most of what we know about the Hedgehog signaling pathway came initially from genetic studies in ____
flies
The effects of Hedgehog are mediated by a latent transcription regulator called ?
Cubitus interruptus (Ci)
In the absence of a ______ signal Ci is ubiquitylated and proteolytically cleaved in proteasomes
Hedgehog signal
In the absence of a Hedgehog signal, Ci is ubiquitylated and proteolytically cleaved in _____
proteasomes
Instead of being completely degraded, Ci is processed to form a _____ ______, and acts as a transcriptional repressor, helping to keep Hedgehog-responsive genes silent.
smaller fragment
smaller fragments formed by Ci acts as?
transcriptional repressor
transcriptional repressor helps to keep ______-_____ genes silent.
Hedgehog-responsive
depends on PKA (protein kinase A) and two kinases (GSK1 and CK1)
processing of Ci protein
Where does the processing of Ci protein depend on
PKA (protein kinase A) and two kinases (GSK1 and CK1)
multiprotein complex includes the protein _____ and a scaffold protein_____?
Fused
Costal2
keep unprocessed Ci out of the nucleus
Fused and a scaffold protein Costal2
Hedgehog functions by blocking the proteolytic processing of Ci, thereby
changing it into a _________ _______
transcriptional activator
Hedgehog functions by blocking the ______ _______
proteolytic processing of Ci
convoluted signaling process that depends on three transmembrane proteins:
Patched,
iHog, and
Smoothened
predicted to cross the plasma membrane 12 times
Patched
on the cell surface and is thought
to serve as a co-receptor for Hedgehog
iHog
-seven-pass transmembrane protein with a structure very similar to a GPCR
-controlled by Patched and iHog.
Smoothened
absence of the signal ____ keep ____ sequestered and inactive
Patched keep Smoothened
inhibits the activity of Patched and induces
endocytosis and degradation
binding of Hedgehog to iHog and Patched
binding of Hedgehog to iHog and Patched inhibits the activity of ____ and induces
________ and ________
Patched
endocytosis
degradation
translocates to the plasma membrane, where it recruits the protein complex containing Ci, Fused, and Costal2.
Smoothened
Smoothened recruits the protein complex containing __,_____,_____
Ci, Fused, and Costal2.
no longer able to bind the other three kinases, and so Ci is no longer
cleaved and can now enter the nucleus and activate the transcription of Hedgehog target genes
Costal
if Costal no longer able to bind the other 3
kinase, Ci no longer _____ and can now enter the nucleus and activate the transcription of _______ ____ ___
cleaved
Hedgehog target genes
increase in Patched protein inhibits further
Hedgehog signalingโproviding another example of negative feedback.
genes for Patched
latent transcription regulators that are present in most animal cells and are central to many stressful, inflammatory, and innate immune
responses.
NFฮบB proteins
excessive ____signaling is found
in a number of human cancers.
NFฮบB
NFฮบB proteins also have important roles during normal animal development: the Drosophila NFฮบB family member
Dorsal
NFฮบB proteins has a crucial role in specifying the _____-____axis of the developing
fly embryo
dorsalโventral
activate the NFKB signaling pathways in animal cells
cell-surface receptors
NFฮบB signaling pathway in Drosophila activated by cell-surface receptors
Toll receptors
cell-surface receptors activate the NFฮบB signaling pathway in vertebrates
Toll-like receptors
Receptors in drosophila and vertebrates that recognize pathogens and activate this pathway in triggering innate immune
responses
Toll receptors in Drosophila and Toll-like receptors in vertebrates
When activated, they trigger a multiprotein ubiquitylation and phosphorylation cascade that releases NFฮบB from an inhibitory protein complex
tumor necrosis factor (TNF ) and interleukin-1 (IL1)
tumor necrosis factor a(TNFa ) and interleukin-1 (IL1) trigger a multiprotein _________ and _______ cascade when activated
ubiquitylation
phosphorylation
When activated, TNFa and IL1 trigger a multiprotein ubiquitylation and phosphorylation cascade that releases NFฮบB from an inhibitory protein complex, so that it can _____ to the nucleus and turn ___ the
transcription of genes that participate in
inflammatory and innate _____ ______
translocate
on
immune responses
five NFฮบB proteins in mammals
RelA, RelB, c-Rel, NFKB1, and NFKB2
Inhibitory proteins that bind
tightly to the dimers and hold them in an inactive state within the cytoplasm of
unstimulated cells
IฮบB
three major IฮบB proteins in mammals
IฮบB ฮฑ, ฮฒ, and ฮต
activated the gene that encodes IฮบBa
NFฮบB
activation of gene that encodes IฮบBa leads to increased synthesis of ____ _____
IฮบBฮฑ protein
binds to NFฮบB and inactivates it, creating a negative feedback loop
IฮบBฮฑ protein
negative feedback that produces two types of NFฮบB responses; induce different patterns of gene expression
TNFa-induced responses
in cells deficient in IฮบBฮฑ, ___ exposure to TNFa produces single, short pulse of ____ activation; turns on gene _
short
NFฮบB
A
produces oscillation in NFฮบB activation; turns on both genes
sustained exposure
hydrophobic signal molecules that diffuse directly across the plasma membrane and bind to intracellular receptors (transcription regulators)
nuclear receptor superfamily
include cortisol, the steroid sex hormones, vitamin D (in vertebrates), and the molting hormone ecdysone (in insects)โare all
made from cholesterol.
steroid hormones
made from the amino acid tyrosine, act to increase the metabolic rate of many
cell types
thyroid hormones
made from vitamin A and
have important roles as local mediators in vertebrate development
retinoids
synthesized in
the skin in response to sunlight
vitamin D
bind to their respective intracellular receptor proteins and alter the ability of these proteins
to control the transcription of specific genes
nuclear receptors
nuclear receptor serves both as intracellular ____ and as intracellular ____
receptors
effectors
their ligand is not known yet
orphan nuclear receptors
bind to specific DNA sequences
adjacent to the genes that the
ligand regulates
nuclear receptors
alters the
conformation of the receptor
protein
ligand binding
ligand binding alters the ______ of the receptor
protein; causing the _____
complex to dissociate; bind
coactivator proteins that stimulate
gene transcription
conformation
inhibitory
Life on Earth possess an _____ _____ that dictates different behaviors at different times of day
internal rhythm
behaviors range from the ____ change in metabolic enzyme activities of a bacterium to the elaborate ____-____cycles of humans.
cyclical
sleepโwake
internal oscillators that control diurnal
rhythms
circadian clocks
enables an organism to anticipate the regular daily changes in its environment and take appropriate action in advance.
Having a circadian clock
timekeepers are ____ cells
individual
controls our diurnal cycles of
sleeping and waking, body temperature, and hormone release
SCN cells in the suprachiasmatic nucleus
of the hypothalamus
SCN cells receive neural cues from
the?
retina
neural cues from the retina send information about the time of day to ___ gland
pineal gland
information to pineal gland relays the time signal to the rest of the body by releasing the hormone _____
melatonin
has the ability to reset in response to light
SCN cells
have similar circadian clock;
can be reset externally imposed light and
dark cycle
Drosophila
generally depend on negative feedback
loops
circadian clocks
oscillations in the activity of an intracellular signaling protein can occur if that protein inhibits its own _____ with a long _____
activity
delay
accumulation of certain gene products
switches ___ the ______ of their own
genes
off
transcription
two transcription regulatory proteins
Tim (timeless) and Per (period)
The mRNAs encoding Tim and Per rise _____ during the day
gradually
Tim (timeless) and Per (period) form a _________
heterodimer
After a time delay, the heterodimer dissociates and Tim and Per are transported into the ____
nucleus
represses the Tim and Per genes
Per
coordinate their activities in response
to the changing conditions of light,
dark, and temperature, which guide the plantโs cycle of growth, flowering, and fruiting
Plant cells
Plant cells also communicate to coordinate activities in their?
roots, stems, and leaves
evolved independently in plants and animals
multicellularity and cell communications
what do plants and animals use for signaling
nitric oxide, cyclic GMP, Ca2+, and Rho family GTPases
no homologs of the nuclear receptor family, Ras, JAK, STAT, TGFฮฒ, Notch, Wnt, or
Hedgehog encoded by the completely sequenced genome of ______ _____
Arabidopsis thaliana
Not encoded by the completely sequenced genome of Arabidopsis thaliana
homologs of the nuclear receptor family, Ras, JAK, STAT, TGFฮฒ, Notch, Wnt, or
Hedgehog
plants do not seem to use _____ ___for intracellular signaling
cyclic AMP
cell-surface receptors in plants are _____-_____
enzyme-coupled
Plants rely largely on a great diversity of transmembrane ____ ____/____ kinases ?
receptor serine/threonine kinases
have a typical serine/threonine kinase cytoplasmic domain and an extracellular ligand-binding domain.
receptor serine/threonine
kinases
receptor serine/threonine
kinases have a typical?
serine/threonine kinase cytoplasmic domain and an extracellular ligand-binding domain.
The most abundant types of receptor serine/threonine kinases have a tandem array of extracellular leucine-rich repeat structures and are therefore called?
leucine-rich repeat (LRR) receptor kinases
How many LRR receptor kinases is encoded by the Arabidopsis genome?
175 leucine-rich repeat (LRR) receptor kinases.
175 LRR receptor kinase in Arabidopsis
Bri1
part of a cell-surface steroid hormone receptor
Bri1
regulate growth and differentiation of plants
brassinosteroids
Binding of a brassinosteroid to a Bri1 cell-surface receptor kinase -> degradation of specific _____ _____ ______
transcription regulatory proteins
brassinosteroid binds to ____ cell-surface receptor kinase
Bri1
help to coordinate plant development
phytohormones, plant growth regulators (plant hormones)
plant growth regulators include?
ethylene, auxin, cytokinin, gibberellins, abscisic acid, brassinosteroids
small molecules made by most plant cells.
Growth regulators
diffuse readily through cell walls and can
either act locally or be transported to influence cells further away
small molecules
- small gas molecule
- promote fruit ripening, leaf abscission, and plant senescence
- function as stress signal in response to wounding, infection, flooding, so on.
ethylene
What does the ethylene promote
fruit ripening, leaf abscission, and plant
senescence
ethylene function as?
stress signal in response to wounding,
infection, flooding
are located in the endoplasmic
reticulum
ethylene receptors
ethylene receptors are located in the _______ _____
endoplasmic
reticulum
dimeric, multipass transmembrane proteins
ethylene receptors
copper-containing ethylene binding domain ; that interacts with a cytoplasmic regions
CTR1
CTR1 stimulates the ubiquitylation and
degradation in proteasomes of nuclear transcription regulator ____
EIN3
CTR1 stimulates the __________ and ________ in proteasomes of nuclear transcription regulator EIN3
ubiquitylation and
degradation
inactivates the receptors, altering their conformation; no longer activated by the genes
ethylene binding
can now activate the transcription of the large number of ethylene-responsive genes
EIN3 protein
EIN3 protein can now activate the transcription of the large number of ______-______ genes
ethylene-responsive genes
indole-3-acetic acid
auxin
helps plants grow toward
light, grow upward rather than branch out, and grow their roots downward.
auxin
auxin regulates organ _____ and _______ and helps plants flower and bear fruit
initiation and positioning
auxin influences ____ _______ by controlling the degradation of transcription regulators.
gene expression
auxin works by stimulating the ubiquitylation and degradation of ______ proteins that block the _______ of auxin target genes in unstimulated cells
repressor
transcription
auxin has its own ______ _____
transport system
move auxin into and out of plant cells, respectively
plasma-membrane-bound influx
transporter proteins and efflux transporter
proteins
can be distributed asymmetrically in the plasma membrane
efflux transporters
highly dynamic and regulated
localization of the auxin
transporters and direction of auxin
flow
A cell can rapidly redistribute transporters by controlling the ______ __ ______
traffic of vesicles
auxin inhibits ____-___ ______
root-cell elongation
light-sensitive proteins
photoproteins
photoproteins sense light by means of a covalently attached light-absorbing _______, which changes its shape in response to light and then induces a change in the proteinโs conformation
chromophore
respond differentially and reversibly to red and far-red light
phytochromes
activates the kinase activity of the phytochrome
red light
inactivates the kinase activity of the phytochrome
far-red light
When activated by red light, the phytochrome is thought to _______ ____ and then
to phosphorylate one or more other proteins in the cell.
phosphorylate itself
In some cases, activated phytochrome activates a latent transcription regulator in the cytoplasm, which then translocates into the nucleus to regulate ____ _______
gene transcription
Plants sense blue light using photoproteins of two other sort?
phototropin and
cryptochromes
- partly responsible for phototropism
phototropin
tendency of plants to grow toward light
phototropism
flavoproteins that are sensitive to blue light
cryptochromes
Cryptochromes are
structurally related to blue-light-sensitive enzymes called photolyases, which
are involved in the repair of?
ultraviolet-induced DNA damage
cryptochromes are also found in
_____, where they have an important role in ____ clocks
animals
circadian
