actin inhibiting agents Flashcards
phalloiden
produced by? function?
death cap mushrooms; poisons by stabalizing actin filaments and keeping them from disassemblig
cytochalasin
function?
binds actin filaments at the barbed ends; remember thats the (+) end
macrolides
made by? bind?
marine sponges; bind actin filaments
what is a job you should never pick up?
mushroom hunting; unless you are starving. in that case I’ll allow it.
how long does mitosis typically take?
the WHOLE cell cycle of a mammalian cell is about 1 day. MITOSIS usually takes about an hour. but it DEPENDs on the cell type
what key concept of S phase should you remember?
there is a cdk (cyclin dependant protein kinase) that allows spindle formation, nuclear envelope to break down. Mr. Cdk is regulated by cyclins. he needs cyclins
what state is a cdk in when it is active
DEphosphorylated. also, attached to a cyclin. therefore, phosphatase activity is critical
microtubules polymer or monomer? subunits? filament name? how many filaments in backbone?
polymer; alpha/beta–beta binds GTP; these subunits connect in head to tail fashion and make protofilaments; usually 13 protofilaments in one filament backbone
uses of microtubules?
tracks for organizing the cell because they have a distinct polarity. used in motility, transportation, chromosome separation
arrangement of microtubules
9+2; use DYENEIN
microtubule turnover?
add at (+) end, lose at (-) end, but actually this probably doesn’t happen in cells
stability of microbule?
DYNAMIC INSTABILITY; it can grow then all of a sudden fall apart really quickly and then start regrowing again; each polymer grows or falls apart at its own rate; this is like little kids with blocks; be able to contrast this with treadmilling;
cap of microtubulin?
GTP cap
centrosome definition?
it controls nucleation, where MTs form, how many MTs there are, determines the polarity of a MT; (-) end of MT anchors at the centrosome
taxol
binds what? stabalizes? derived from? used for?
microtubules; stablizes or blocks MTs and keeps cells from dividing (antimitotic); from the pacific yew tree; used as an anticancer drug. probably the frontline drug for SOLID tumors (ovarian, breast, lung, bladder, prostate)
where does taxol bind?
GTP cap to stabalize it, and blocks transition from GTP to GDP loaded
control point of MT?
its easy to elongate a MT, but hard to start one. so, the seed formation is the limiting factor
how could you make MTs form more quickly?
add gamma tubulin in the presence of tubulin heterodimers.
compare nucleators in actin vs MT
actin: arp2/3 complex and formin
MT: gamma tubulin
where does gamma tubulin bind?
at the minus end. that makes sense because its a nucleator.
what does gamma tubulin DO to start a MT
associates with gamma TuRC in a “lock washer” configuration; typically there are 13 gamma tubulins that correspond to 13 things. i missed it
what is a MTOC
a centrOSOME
where are centrIOLES
in the centrOSOME, (at the bottom of an axon, or in a basal body, or in a spindle pole)
what is the structure of the centrIOLE
they are 9+THREEEE!!! (the other one is 9+2); it has gamma tubulin and gamma TURK thing
what is PCM
paracentriolar fuzz
where is centrOSOME
at spindle poles of mitotic spindle apparatus
again, what end is at the centrOSOME
the MINUS!!!!
at s to G2 transition what happens to centRIOLES
duplicates and separates (2 to 4). the paracentriolar fuzz does the same. one pole becomes the “north pole” the other becomes the “south pole”
centrOSOME cycle
in addition to the anaphase, telophase, etc cell cycle
what do yo uneed to build a spindle?
microtubules, spindle poles(centrosomes), microtubule motors, chromosomal attachment sites
name the 3 pieces/parts of the spindle apparatus
ASTRAL MTS: make contact with the periphery of the cell ** important for position
INTERPOLAR MTS: these cross in the middle in antipolar way. stabalize the distance between centrosomes
KINETOCHORE MTS: these meet in the middle with motors
what word should you be able to spell
kinetochore
what are the two motor types for microtubules?
kinesin; dynein
what directon does a dynein motor crawl?
dynein is dying, he is pessimistic. he goes to the negative end
what direction does a kinesin motor crawl?
conventionally, they go +. BUT really they swing both ways. if the motor is at the C-terminus, then it goes toward the negative end. if the motor is in the middle, then they actually aren’t motors, they dissassemble MTS
function of kinetochore
captures the chromosome. also, it regulates the behavior of things that you don’t really have to memorize. know that its a multiprotein complex machine
after a kinetochore captures a chromosome what happens
there should be a balance of forces between:
plus end binding proteins, plus end polymerizing proteins (CLASPS), and depolymerizing kinesins to drive disassembly of MTS
moving to the poles. what are the 3 phases?
anaphase A: you pull the kinetochore MTs apart
anaphase B: you push the centrosomes apart with the overlap MTs and their motors
anaphase C: you pull the centrosomes toward the cell wall with the astral MTs
how do you do the metaphase to anaphase transition
use APC (anaphase promoting complex, or cyclosome) it is a ubiquitinizing thing that sends the CDK (remember CDK started this whole ordeal) to a proteasome
sister chromatids are held together?
at the equitorial plate in the nucleus by a protein complex called the cohesion complex that is the protein glue that holds them together. they are drawn as loops around the centers of the sister chromatids together.
what is separase?
this guy is a protease that targets the cohesin complex that connects sister chromatids and allows them to separate
securin?
is the little guy that holds onto separase and keep him inactive until he needs to separate the sister chromatids
if you don’t have good metaphase to anaphase transition, what can be a problem?
non-disjunction diseases like trisomy 21 (downsyndrome)
