Abstract
The signal-transducing guanine nucleotide-binding regulatory (G) proteins are heterotrimers composed of three subunits - α, β, and γ. Although multiple distinctive forms of the α subunit have been described, only two forms of the β subunits of the G proteins have been identified. To investigate further the structural diversity of the β subunits, we screened bovine and human retina cDNA libraries and isolated clones encoding three distinct types of G protein β subunit. One form was identical to previously isolated β1-subunit cDNA clones that encode the 36-kDa form of the β subunit, whereas a second form was identical to previously described β2 cDNAs that encode the 35-kDa β isoform. In addition, we identified another species, designated β3 subunit, which encodes a third distinct form of the β subunit. The β3-subunit cDNA corresponds to a 2.0-kilobase mRNA expressed in all tissues and clonal cell lines examined. Nucleotide sequence analysis indicates that the encoded peptide consists of 340-amino acid residues with a Mr of 37,221. The amino acid sequences of the three β subunits are closely related: 83% identity between β1 and β3 subunits and 81% identity between β2 and β3 subunits. By contrast, the 3′-untranslated regions of the three cDNAs show no significant homology. Our data support the hypothesis that a family of β-subunit polypeptides exists and extend understanding of β-subunit structure.
Original language | English (US) |
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Pages (from-to) | 2329-2333 |
Number of pages | 5 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 87 |
Issue number | 6 |
State | Published - Mar 1990 |
Externally published | Yes |
Keywords
- Molecular cloning
- Signal transduction
ASJC Scopus subject areas
- General