Characterization of the cDNA and Genomic Sequence of a G Protein γ Subunit (γ₅)

Abstract

A cDNA from human placenta and liver tissues that contained both sequence for the lysosomal glycosidase di-N-acetylchitobiase and sequence homologous to the γ subunit of GTP-binding proteins was previously isolated. Here we have shown that the γ-subunit-homologous portion of this unusual cDNA is derived from a member of the γ-subunit multigene family. The partial human γ-subunit sequence was used to isolate the corresponding full-length cDNA clones from bovine and rat livers. The two cDNAs encode identical 68-amino-acid proteins (7.3 kDa) homologous to previously cloned G protein γ subunits. The bovine gene sequence encoding this new γ-subunit isoform (γ₅) was determined and found to have an intron-exon structure consistent with the original human chitobiase–γ₅-subunit hybrid mRNA being a product of alternative splicing. Genomic cloning also resulted in the isolation of a human γ₅ pseudogene.