HOMOLOGOUS AND UNIQUE G-PROTEIN ALPHA SUBUNITS IN THE NEMATODE CAENORHABDITIS-ELEGANS

A cDNA corresponding to a known G protein alpha subunit, the alpha subunit of G(o) (G(o)alpha), was isolated and sequenced. The predicted amino acid sequence of C. elegans G(o)alpha is 80-87% identical to other G(o)alpha sequences. An mRNA that hybridizes to the C. elegans G(o)alpha cDNA can be detected on Northern blots. A C. elegans protein that crossreacts with an antibovine G(o)alpha antibody can be detected on immunoblots. A cosmid clone containing the C. elegans G(o)alpha gene (goa-1) was isolated and mapped to chromosome I. The genomic fragments of three other C. elegans G protein alpha subunit genes (gpa-1, gpa-2, and gpa-3) have been isolated using the polymerase chain reaction. The corresponding cosmid clones were isolated and mapped to disperse locations on chromosome V. The sequences of two of the genes, gpa-1 and gpa-3, were determined. The predicted amino acid sequences of gpa-1 and gpa-3 are only 48% identical to each other. Therefore, they are likely to have distinct functions. In addition they are not homologous enough to G protein alpha subunits in other organisms to be classified. Thus C. elegans has G proteins that are identifiable homologues of mammalian G proteins as well as G proteins that appear to be unique to C. elegans. Study of identifiable G proteins in C. elegans may result in a further understanding of their function in other organisms, whereas study of the novel G proteins may provide an understanding of unique aspects of nematode physiology.