Guanylate cyclase–activating proteins, 

bind to guanylate cyclase and stimulate its activity, elevating cGMP level and causing the cGMP-gated ion channels to reopen.

TLS Online TPP Program

#Id: 9060

#XL - T Zoology

Increased cAMP; PKA active, increased glycogen breakdown, and decreased glycogen synthesis

TLS Online TPP Program

#Id: 9061

#XL - T Zoology

The GPK in skeletal muscle is a huge protein with multiple subunits:

Kinase subunit contains the catalytic activity that activates GP 

Regulatory subunits is the ubiquitous protein calmodulin

TLS Online TPP Program

#Id: 9062

#XL - T Zoology

GPK enzyme activity is increased either by phosphorylation of these two regulatory subunits by PKA or by Ca+2 binding to the calmodulin subunit; maximal activity requires both.

TLS Online TPP Program

#Id: 9063

#XL - T Zoology

Phosphorylation of PKA at threonine-197 leads to conformational change in the activation loop, that promotes binding of both ATP and its substrate proteins.

PKA can autophosphorylate itself on T197

TLS Online TPP Program

#Id: 9064

#XL - T Zoology

The activities of GPK and GP are inhibited by a phosphatase called phosphoprotein phosphatase.

TLS Online TPP Program

#Id: 9065

#XL - T Zoology

The promoter or enhancer segments of all genes regulated by PKA contain a cis-acting DNA sequence, the cAMP-response element (CRE), which

contains the highly conserved nucleotide sequence,

5'-TGACGTCA-3'.