BMB Exam 1: Enzyme-coupled receptors/Scaffold Proteins/Interaction Domains

Enzyme-coupled receptors

enzymatic activity or are associated with enzymes. (Most of them are kinases or associate with kinases)

function of Enzyme-linked receptors

- often involved in cell growth & movement

- ligands typically = growth factors

some attached to cell surface

- cytosolic receptor domain = enzyme or directly associates with enzyme

- genetic defects can lead to uncontrolled cell proliferation

6 classes of enzyme-linked receptors

•Tyrosine kinases

•Tyrosine kinase-associated

•Tyrosine phosphatases

•Serine/threonine kinases

•Histidine-associate kinase

•Guanylyl cyclase

Receptor Tyrosine Kinases (RTKs)

secreted peptide growth factors and peptide hormones

- extracellular ligand-binding domain

- single transmembrane domain

- intracellular tyrosine kinase domain

- activation of the receptor induces a conformational change, which causes receptors to dimerize

- two kinase domains brought together by dimerization activate each other

- phosphorylation activates kinase activity of RTK

where are other ligands bound to?

cell surface upon which the target cell crawls

Ephrin receptor - ephrin interaction is involved in ________-_________ signaling

contact-dependent

Eph receptors are (1)____

- largest class of membrane-bound ligands

- help guide migration of ___ & _____; important in development

(1) RTKs

(2) cells & axons

Ephrin receptor

Act both ways: activated Eph receptors are transmitting signal back to signaling cell

- behavior of both signaling cell and target cell are altered

*bidirectional signaling is important..?

to prevent cells of different tissues from mixing

Which of the following usually goes both ways (signaling cell-target cell and target cell-signaling cell)?

•A. Any receptor tyrosine kinase signaling

•B. Signaling through Ephrins

•C. Signaling through GPCRs

•D. All of the above

•B. Signaling through Ephrins

Cross-phosphorylation stimulates kinase activity & creates high affinity _________ ______ for other proteins

docking sites

_________ _______ prevent cross-talk between parallel MAP kinase molecules

scaffold proteins

role of scaffold proteins

organize multiple signaling proteins into larger complexes; enhancing SPEED, EFFICIENCY, AND SPECIFICITY; bring the kinases into close proximity

Sometimes an _______ (_________) __________ can function as a scaffold protein

activated (phosphorylated) receptor

A single extracellular signal can initiate multiple distinct signal transduction cascades, leading to _________ ________.

multiple outcomes (i.e, change in cell shape, and cell movement)

Proteins with _____ or ______ interaction domains bind to phosphorylated tyrosines at RTKs

SHR or PTB

which protein domain is the most common?

SH2

- can recognize phosphorylated tyrosines

- can be inserted anywhere in the protein without disturbing its structure and function

- link RTKs to different signaling pathways

the assembly of signaling complexes depends on __________ __________

- they are compact

- bind to certain structural motifs

interaction domains

interaction domains of signaling proteins are _________ ___________

highly conserved