Isolation and expression of a novel chick G-protein cDNA coding for a G alpha i3 protein with a G alpha 0 N-terminus.
We have cloned cDNAs coding for G-protein alpha subunits from a chick brain cDNA library. Based on sequence similarity to G-protein alpha subunits from other eukaryotes, one clone was designated G alpha i3. A second clone, G alpha i3-o, was identical to the G alpha i3 clone over 932 bases on the 3' end. The 5' end of G alpha i3-o, however, contained an alternative sequence in which the first 45 amino acids coded for are 100% identical to the conserved N-terminus of G alpha o from species such as rat, mouse, human, bovine and hamster. Both clones were found to be expressed in all tissues studied. The unusual alpha o-alpha i3-like G-protein chimera, G alpha i3-o, was found to be expressed at significantly lower levels than G alpha i3. In vitro transcription and translation of the G alpha i3-o cDNA clone gave a protein of approx. 41 kDa which stably bound guanosine 5'-[gamma-thio]triphosphate. G alpha i3-o appears to be the first G-protein alpha subunit cloned which contains ends that are homologous to two different alpha subunit isoforms, G alpha o and G alpha i3.
Kilbourne
E J
EJ
Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115.
Galper
J B
JB
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain; D002645:Chickens; D003001:Cloning, Molecular; D018076:DNA, Complementary; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D015870:Gene Expression; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D012333:RNA, Messenger / Q000235:genetics; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D018076:DNA, Complementary; D012333:RNA, Messenger; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins