role of phosphorylation in cell signalling

Question 1

which types of kinase are involved in cell signalling?

Answer 1

tyrosine kinases - e.g. EGF receptor, PDGF receptor, insulin receptor
serine/threonine kinase - e.g. PKA, protein kinase C, CaM, PKB

Question 2

how does phosphorylation by RTKs facilitate signal transduction?

Answer 2

creates phosphotyrosine docking sites for various intracellular signalling proteins that relay the signal

Question 3

how can phosphorylation of RTKs be detected?

Answer 3

• stimulate with growth factor
• detect using anti-phosphotyrosine antibody
• perform a western blot

Question 4

how is cross-phosphorylation of RTK subunits facilitated?

Answer 4

each arm contains its own tyrosine kinase domain

Question 5

how is EGFR activated?

Answer 5

the dimerisation event orients the internal kinase domain into an asymmetric dimer, where one kinase is pushed against the other. this causes a conformational change, activating the receiver

Question 6

how do signalling proteins recognise a specific phosphotyrosine residue on a protein rather than just any phosphotyrosine?

Answer 6

the PTB domain recognises surrounding features of the polypeptide chain in addition to the phosphotyrosine itself

Question 7

give examples of PTB domains

Answer 7

phospholipase C, phosphoinositide 3-kinase

Question 8

what is conserved amongst PTBs?

Answer 8

SH2 domain for phosphotyrosine binding