G alpha i-G alpha s chimeras define the function of alpha chain domains in control of G protein activation and beta gamma subunit complex interactions.
Gs and Gi2 are G proteins whose alpha subunits are 65% homologous. Within the 355 amino acid alpha i2 polypeptide, substitution of residues Ile213-Lys319 with the corresponding alpha s region (Ile235-Arg356) generated a chimera that activated adenylyl cyclase, indicating that the alpha s activation domain resides within this 122 amino acid alpha s sequence. Mutation within alpha s residues Glu15-Pro144 resulted in an alpha s polypeptide having an enhanced rate of GDP dissociation. Mutation within two regions of the N-terminus influenced the ability of pertussis toxin to ADP-ribosylate the alpha subunit polypeptide, a reaction controlled by the beta gamma subunit complex. The findings define the G protein alpha subunit N-terminus as a regulatory region controlling beta gamma subunit interactions and GDP dissociation independent of the GTPase and effector activation domains.
Osawa
S
S
Division of Basic Sciences, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
Dhanasekaran
N
N
Woon
C W
CW
Johnson
G L
GL
D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002678:Chimera; D002772:Cholera Toxin / Q000378:metabolism; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D037342:Pertussis Toxin; D015183:Restriction Mapping; D014162:Transfection; D010566:Virulence Factors, Bordetella / Q000378:metabolism
D037361:Adenylate Cyclase Toxin; D046911:Macromolecular Substances; D015345:Oligonucleotide Probes; D010566:Virulence Factors, Bordetella; D002772:Cholera Toxin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases