title: GTP analogue hydrolysis by the Gs protein: implication for the role of catalytic glutamine in the GTPase reaction.
abstract: Hydrolysis of GTP, bound to members of the G-protein superfamily, terminates their downstream signaling activity. A conserved glutamine serves a critical role in this pivotal guanosine triphosphatase (GTPase) reaction. However, the role of the catalytic glutamine in GTP hydrolysis is still not well understood. We have employed substrate-assisted catalysis to probe the catalytic mechanism of Gs alpha using GTP analogues. These GTP analogues, each having different functional groups, were designed to support or refute particular putative GTPase mechanisms. We have found that a hydrogen donor group, in close proximity to the gamma-phosphate of GTP, is necessary and sufficient to substitute for the function of the catalytic glutamine in the GTPase reaction.
authors.affiliation: Department of Biological Chemistry and the Kuhne Minerva Center for Studies of Visual Transduction, The Hebrew University of Jerusalem, Israel.
authors.forename: T
authors.initials: T
authors.lastname: Zor
authors.forename: R
authors.initials: R
authors.lastname: Andorn
authors.forename: I
authors.initials: I
authors.lastname: Sofer
authors.forename: M
authors.initials: M
authors.lastname: Chorev
authors.forename: Z
authors.initials: Z
authors.lastname: Selinger
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000378:metabolism*; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000737:chemistry / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D010306:Parotid Gland / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity
chemical_list: D005973:Glutamine; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D020558:GTP Phosphohydrolases; D019205:GTP-Binding Protein alpha Subunits, Gs; D000262:Adenylyl Cyclases