Flashcards in Chapter 3- Nonenzymatic Protein Function and Protein Analysis Deck (42)
repetitive organization of secondary structural elements together
primary structural proteins in body
collagen, elastin, keratin, actin, and tubulin
trihelical fiber (3 a-helices woven together to form a secondary helix). provides strength and flexibility---ex: makes up most of extracellular matrix of connective tissue
extracellular matrix of connective tissue. stretch and recoil like a spring.
intermediate filament proteins found in epithelial cells. mechanical integrity of cell and also function as regulatory protein.----- primary protein in hair and nails
protein that makes up microfilaments and thin filaments in myofibrils. MOST ABUNDANT PROTEIN IN EUKARYOTIC CELLS.
protein that makes up microtubules. provide structure, chromosome separation in mitosis, and intracellular transport with kinesin and dynein. has polarity.
kinesins and dyneins
motor proteins associated with microtubules. have 2 heads, one is always attached to tubulin at all times. important for vesicle transport in the cell.
play key roles in aligning chromosomes during metaphase and depolymerizing microtubules during anaphase of mitosis. bring vesicles toward positive end of microtubule (ex: toward synaptic terminal in neurons)
involved in sliding movement of cilia and flagella. bring vesicles toward negative end of microtubules (ex: back to soma in neurons).
examples of binding proteins
hemoglobin, Ca2+ binding proteins, DNA-binding proteins.
Cell adhesion molecules (CAMs)
proteins found on the surface of most cells that aid in the binding of the cell to the extracellular matrix. all integral membrane proteins.
3 types of adhesion molecules
group of glycoproteins that mediate Ca2+ dependent cell adhesion. hold similar types of cells together (ex: epithelial cells)
group of proteins that all have two membrane-spanning chains called a and B. important for binding and communication w/ extracellular matrix. cellular signaling (promoting division or apoptosis). also stabilize clots
bind to carbohydrate molecules that project from other cell surfaces. weakest bonds formed by the CAMs . expressed on white blood cells and endothelial cells that line blood vessels.
3 ourcomes when antibodies bind to their targets (antigens)
1. neutralize antigen
2. opsonization (marking pathogen for destruction by other white blood cells immediately
3. agglutinating (clumping together) the antigen and antibody into large insoluble protein complexes that can be phagocytized and digested by macrophages.
3 types of ion channels
1. ungated (unregulated)
2. voltage-gated (regulated by membrane potential change)
3. ligand-gated (binding specific substance or ligand to channel for it to open or close)
3 primary protein domains.
1. membrane-spanning domain (anchors the receptor in the cell membrane)
2. ligand-binding domain (stimulated by the appropriate ligand and induces a conformational change that activates the catalytic domain)
3. catalytic domain (once activated, typically initiates a second messenger cascade)
G-protein coupled receptors
integral membrane proteins involved in signal transduction
heterotrimeric G protein
used by G-protein coupled receptors to transmit signals to an effector in the cell. 3 subunits (a, B, gamma)
3 main types of G proteins
1. Gs stimulates adenylate cyclase- increases levels of cAMP
2. Gi inhibits adenylate cyclase- decreases levels of cAMP
3. Gq activates phospholipase C- cleaves phospholipid from the membrane to form PIP2. PIP2 is then cleaved into DAG and IP3. IP3 can open Ca2+ channels in ER increasing Ca2+ levels in the cell.
inactive form of G protein
a subunit binds to GDP in complex with B and gamma
active form of G protein
ligand binds to GPCR, receptor becomes active, GDP is replaced with GTP, a-subunit is able to dissociate from B and gamma subunits, a-sub alters activity of adenylate cyclase. then GTP becomes dephosphorylated to GDP then B and gamma-sub rebind to a-sub rendering G protein inactive.
how are proteins/ biomolecules isolated from body tissues or cell cultures
lysis and homogenization (crushing, grinding, blending) tissue of interest into an evenly mixed solution, then centrifugation will isolate proteins
most common isolation techniques
electrophores and chromatography
subjecting compounds to an electric field, which moves according to their net charge and size.
method for analyzing proteins in their native states. limited to mass-to-charge and mass-to-size ratios. most useful to compare the molecular size or charge of proteins known to be similar in size from other analytic methods.
separates proteins based on mass alone. denatures the protein.