A system to unambiguously describe the configurations of molecules with more than one asymmetric center was devised in 1956 by Robert Cahn, Christopher Ingold, and Vladimir Prelog. In the Cahn–Ingold– Prelog or RS system

TLS Online TPP Program

#Id: 9469

#Unit 4. Cell Communication and Cell Signaling

IL-2 receptor complex activates

STATs 1, 3, and 5 but not STATs 2 or 4

TLS Online TPP Program

#Id: 9470

#Unit 4. Cell Communication and Cell Signaling

Phosphorylated STAT dissociates spontaneously from the receptor, and two phosphorylated STAT proteins form a homodimer.

TLS Online TPP Program

#Id: 9471

#Unit 4. Cell Communication and Cell Signaling

STAT5 becomes activated in erythroid progenitor cells and induces expression of the protein Bcl-xL.

TLS Online TPP Program

#Id: 9472

#Unit 4. Cell Communication and Cell Signaling

Two mechanisms for terminating cytokine signaling:

1. Short-term regulation: SHP1

2. Long-term regulation: SOCS proteins

TLS Online TPP Program

#Id: 9473

#Unit 4. Cell Communication and Cell Signaling

SHP1 a phosphotyrosine phosphatase, contains:

SH2 domain  & Phosphatase domain

TLS Online TPP Program

#Id: 9474

#Unit 4. Cell Communication and Cell Signaling

SHP1 

Binding of an SH2 domain to a phosphotyrosine in the activated receptor unmasks its phosphatase catalytic site