lecture 11

signal transduction

conversion of information into a chemical change

pH, osmolarity, food availability, predators, light, oxygen, etc.

things that change we want to communicate

universal

signal transduction is a ______ proerpty in all cells

precise

there is a ____ molecular complementarity between signal and receptor

complementary; do not

Signal molecule fits binding site on its _______ receptor; other signals _____ (do/do not) fit

sensitivity

_______ = high affinity + cooperativity + amplification of signal

cooperativity

one binding event can induce another is due to ______

large; small

Cooperativity in receptor-ligand interactions results in ____ (large/small) changes in receptor activation with _____ (large/small) changes in ligand concentration 

amplification

when enzymes activate enzymes, the number of affected molecule increases in an enzyme cascade

desensitization/adaptation

receptor activation triggers a feedback circuit that shuts off the receptor or removes it form cell surface

integration

ability of system to receive multiple signals and produce a unified response based on all info

weak

precise molecular complementarity between signal and receptor is mediated by ______ interactions

G protein–coupled receptors (GPCRs)

receptors that are closely associated with a member of the guanosine nucleotide–binding protein (G protein) family

seven; GTP, GDP; regulated, activated G protein

Three essential components define signal transduction through GPCRs:

(1) a plasma membrane receptor with _____ transmembrane helical segments

(2) G protein that cycles between active (_____-bound) and inactive (_____-bound) forms

(3) an effector enzyme (or ion channel) in the plasma membrane that is _____ by the _____ _____ _____

cAMP, cGMP, Ca2+, IP3

example of intracellular second messengers

alpha, beta, gamma

3 components of the g protein

350

human genome has approx ___ GPCRs

GDP, GTP

in g proteins, the occupied receptor causes replacement of ____ bound to Gs by _____ activating Gs

receptor tyrosine kinases

plasma membrane receptors w/ intrinsic protein kinase activity

extracellular; inside

receptor tyrosine kinases transduce ____ signals to the _____ of the cell

monomers

receptor tyrosine kinases found as _____ in inactive form

phosphorylated

the activated tyrosine-kinase is a _________ dimer

ligand

extracellular domain of receptor tyrosine kinase binds _______

cytoplasmic; tyr

for receptor tyrosine kinases: the ________ domain is a protein kinase that phosphorylates _____ residue on specific target proteins

receptor guanylyl cyclase

receptor enzyme that converts GTP to cGMP (second messenger)

extracellular; intracellular

receptor guanylyl cyclases contain a ______ ligand-binding domain and a ______ catalytic domain

no

there exist a soluble ____-activated guanylyl cyclase

nuclear receptors

proteins in the nucleus that respond to steroid hormones, retinoic acid, thyroid hormone

gene expression

nuclear receptors alter ___ ______ directly upon binding ligand