Characterizing the interactions between the two subunits of the p101/p110gamma phosphoinositide 3-kinase and their role in the activation of this enzyme by G beta gamma subunits.
Recently, we have reported the purification and cloning of a novel G protein betagamma subunit-activated phosphoinositide 3-kinase from pig neutrophils. The enzyme comprises a p110gamma catalytic subunit and a p101 regulatory subunit. Now we have cloned the human ortholog of p101 and generated panels of p101 and p110gamma truncations and deletions and used these in in vitro and in vivo assays to determine the protein domains responsible for subunit interaction and activation by betagamma subunits. Our results suggest large areas of p101 including both N- and C-terminal portions interact with the N-terminal half of p110gamma. While modifications of the N terminus of p110gamma could modulate its intrinsic catalytic activity, binding to the N-terminal region of p101 was found to be indispensable for activation of heterodimers with Gbetagamma.
Krugmann
S
S
Signalling Programme, The Babraham Institute, Babraham, Cambridge CB2 4AT, United Kingdom. sonja.krugmann@bbsrc.ac.uk
Hawkins
P T
PT
Pryer
N
N
Braselmann
S
S
D000818:Animals; D001665:Binding Sites; D019281:Dimerization; D004789:Enzyme Activation; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009504:Neutrophils / Q000201:enzymology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D017384:Sequence Deletion; D013552:Swine
C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D011994:Recombinant Proteins; D019869:Phosphatidylinositol 3-Kinases; D019204:GTP-Binding Proteins; D020962:Heterotrimeric GTP-Binding Proteins