Important Proteins Flashcards
Glycosaminoglycans (GAGs)
Link to core proteins in the interstitial ECM to form proteoglycans
Glycoproteins
Fibrous proteins in the interstitial ECM
Collagen
A protein that provides tensile strength in connective tissues (bone, skin, hair, nails)
Collagen
A protein that provides tensile strength in connective tissues (bone, skin, hair, nails)
Triple helix
Pre procollagen
The cytoplasmic form of collagen
N proteinase
Cleaves the N terminus of procollagen extracellulary
Confers ability to assembly into collagen fibres
C proteinase
Cleaves the C terminus of procollagen extracellularly
Confers ability to assembly into collagen fibres
Proteoglycans
Extracellular proteins linked to glycosaminoglycans in the interstitial ECM
Collagen type4
Forms the basal lamina with laminin
Laminin
Forms the basal lamina with collagen type 4
Laminin
Forms the basal lamina with collagen type 4
Organises the sheet
Triple helix with a cross
Nidogen and perlecan
Hold the basal lamina together
Collagen type4
Forms the basal lamina with laminin
GlyXY repeats confer bendiness
Laminin
Forms the basal lamina with collagen type 4 Organises the sheet Triple helix with a cross 15 isoforms Self assembles
Nidogen and perlecan
Hold the basal lamina together
Laminin and collagen 4 sheets cross linkage
Integrins
Transmembrane receptors that couple the matrix to the cytoskeleton
Talin and vinculin
Actin binding proteins ABPs
N-CAM
Adhesion molecule in neural crest cells
Laminin and fibronectin
Cause neural crest cells to migrate
Tether proteins
Aid membrane fusion
Exchange factors
Involved in cell signalling
Sorting signals
Amino acid labels that tell a protein where to be transported
Signal peptidases
Remove the sorting signals after transport
Nuclear pore proteins
30 proteins make a ‘basket’
Only 5 types of proteins:
- Annular subunits (central)
- Lumenal subunits (TM)
- Ring subunits (faces)
- Fibrils (FG repeats)
- Nuclear basket
Transcription Factors
Proteins which activate gene expression and bind to specific promotor regions
Nuclear localisation signals
Positively charged residues that tell a protein to go into the nucleus
Karyopherins, Importins
Nuclear localisation signals
Nuclear import adaptor proteins
Receptor is binding another protein (an adaptor) that bind the protein
Ran
Small GTPase - molecular switch with two states, active (GTP cound) inactive (GDP bound)
GAPs
GTPase activating proteins
Switch Ran OFF
By increasing rate of GTP hydrolysis
GEFs
Guanine nucleotide exchange factors
Turn Ran ON
By increasing rate of GDP-GTP exchange
Chaperones
Are proteins that bind and block polypeptide folding
Hsp70
Chaperone protein family in mitochondria
TOM
Translocator outer mitochondrial membrane complex
TIM
Translocator inner mitochondrial membrane complex
Pex 5 and Pex 7
Involved in Peroxisome biogenesis
Catalase
Enzyme in peroxisomes Degrades H202 produced by Oxidases
Oxidase
Produces H202 in peroxisomes
26S proteosome
Degrades Pex5
Pex1 and 6
Form the lever arm for transient pore model
ATPases
SRP
Signal recognition particle
Made out of RNA and 6 proteins Hydrophobic pocket lined with methionines recognises N terminus signal sequence
Has a translational pause domain (like a finger that stops the ribosome translating) Brings the ribosome to the ER SRP binds to SRP receptor in the ER membrane
Sec61
Protein translocator in the ER Hetero trimeric complex
Bundled alpha helices with a central pore Pore is usually closed by a small a-helix ‘plug’ Signal peptide displaces the plug allowing transport of the protein
NO synthase
Makes nitric oxide
Is used as a signal to relax smooth muscle in blood vessels
Connexins
6 subunit protein that forms GAP junctions (small channels in cell membranes)
Twist open or closed
G protein coupled (GPCRs)
Receptors have 7 transmembrane domains (serpentine)
Ligand binds, complexes with trimeric G proteins (alpha beta gamma subunits)
Activate an enzyme at the plasma membrane
Transmits a signal
e.g generation of cAMP by adenylyl cyclase
Receptor Tyrosine Kinases
Form dimers in the membrane
Activates phosphorylation domains in the cytosol
Beginning of signal transduction cascade
Phosphatases
Enzymes that dephosphorylate (kinase antagonists)
Adenylyl cyclase
Membrane bound enzyme Produces cAMP from ATP
Activated by G proteins
Phosphodiesterases
Enzyme that converts cAMP to AMP
Protein Kinase A (PKA)
Phosphorylates Two kinds of target proteins: Fast (phosphodiesterase switch) Slow (CREB (dna transcription))
AKAPs
A kinase anchoring proteins A group of proteins which bind the regulatory subunit of protein kinase A (PKA) and confine the holoenzyme to discrete locations within the cell
Calmodulin
Protein which changes conformation allosterically when bound to Ca2+ Needs 2 Ca2+ to bind Targets CAM kinases
Hb also does this allosteric change
CAM kinases
Autophosphorylate So even when Ca2+ is lost, the signal is active until phosphatases overwhelm it
mTOR
Cytoplasmic Kinase
Phosphorylates Ser/Thr residues
RHEB
Ras family small GTPase
TSCs
Tuberous Sclerosis Complex
AKT/Protein kinase B (PKB)
A serine/threonine-specific protein kinase that plays a key role in multiple cellular processes such as glucose metabolism, apoptosis, cell proliferation, transcription and cell migration
mTORC1
Promotes protein synthesis
Promotes ribosome production
Inhibits protein degradation
mTOR pathway
mTORC2
Changes actin cytoskeleton and cell shape
mTOR pathway
elF4E
Translation initiation factor
Indirectly activated by mTOR by inhibiting an inhibitor of elF4E
S6 kinase
Phosphorylates ribosomal protein S6
Increases translation of ribosomal components
mTOR pathway
Cdc42
Rho family GTPase
Central regulator of cell polarity
Recruits many proteins involved in actin, MTs, trafficking and cell junctions
Caspases
Protease enzymes in apoptosis
TNF
Tumour necrosis factor
Cell signaling protein (cytokine) involved in systemic inflammation and is one of the cytokines that make up the acute phase reaction
Produced chiefly by activated macrophages, although it can be produced by many other cell types such as CD4+ lymphocytes, NK cells, neutrophils, mast cells, eosinophils, and neurons
Fas
The Fas receptor is a death receptor on the surface of cells that leads to programmed cell death (apoptosis)
FADD, TRADD
Fass associated death domain protein
TNF type 1 death domain protein
Bcl proteins
B cell lymphoma 2
Involved in intrinsic apoptosis, either pro or anti apoptotic
BH123
Pro apoptotic Bcl protein on mitochondrial membrane
Bcl 2
Anti apoptotic Bcl protein, inhibits BH123
BH3 proteins
Pro apoptotic protein that binds Bcl2
Apaf1
Apoptotic protease activating factor
in mitochondria
Apoptosome
Oligomer of 7 Apaf1 proteins with bound Cyt c
Plus a central procaspase9
IAPs
Inhibitors of apoptosis
BIR domain binds caspases
Anti IAPs
Block IAPs
Mitochondria
Jnk
Stress activated MAP kinase
Causes transcription of BIM and this apoptosis
Bid, Bim and Puma
Potent activators of apoptosis
Inhibit all Bcl2 family
Formin
Nucleates straight actin (bundled), remains at plus end
ARP2/3 complex
Nucleates branched actin (lamellipodia), remains at minus end
Profilin
Pro- actin formation, binds subunits and speeds up
Thymosin
Binds subunits and prevents actin formation
Cofilin
Binds actin at the minus end, speeds up disassembly
Gelsolin
Severs actin filaments and binds to plus end
Capping protein
Prevents assembly and disassembly at actin plus end
Tropomyosin
Stabilizes actin filament
Fimbrin, alpha actinin, filamin, spectrin,ERM
Proteins that bundle, cross link and attach actin to the membranes
Par proteins
Kinases
Cause asymmetric positioning of the mitotic spindle
Polarise the cell
Scribble and Crumbs
Organise polarity of cells to the basal lamina with Par proteins
Lkb1
Human gut par protein, mutations cause polyps
Centrosome
Nucleates microtubules
Centriole
MT organising centre
mother and daughter
same structure as the basal body
Spindle pole body
Centriole equivalent in yeast
Nexin
Connects double MT in outer ring of flagella
Important in flagella wave form - causes MT to bend
Centrin
Structural protein found in the basal body
Controls basal body number (mutants have too many, vfl mutant)
PitX2
Transcription factor positioned by ciliary beating during embryogenesis
Gene regulatory proteins
Bind directly or indirectly to the regulatory DNA adjacent to the genes that are to be controlled
Protists are far more diverse than
multicellular animals, plants and fungi
anatomy is elaborate with sensory bristles, beating cilia, mouth parts and contractile bundles
Allow distant evolutionary past to be put in context by genome analysis
Saccharomyces cerevisiae is a good model organism because
It has a very small eukaryotic genome
robust and easy to grow, grows rapidly
can divide asexually or sexually, and can be induced
good for studying cell cycle - highly conserved