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Published September 2, 1994 | metadata_only
Journal Article

A Fifth Member of the Mammalian G-Protein β-Subunit Family. Expression in brain and activation of the β2 isotype of phospholipase C.


The β-subunits of the heterotrimeric GTP-binding proteins (G-proteins) are important regulators of G-protein α-subunits as well as of certain signal transduction receptors and effectors. We have identified a fifth member of the G-protein β-subunit family, Gβ5, by molecular cloning. Sequence analysis of recombinant clones revealed an open reading frame of 1,059 base pairs, potentially encoding a protein of 353 amino acids having 53% identity to previously identified Gβ-subunit proteins. Northern blot analysis of poly(A)-selected mRNA prepared from different mouse tissues demonstrated that Gβ5 is predominantly expressed in adult brain as two transcripts of 2.3 and 1.75 kilobases. A Gβ5-specific antiserum detected a band of 39.3 kilodaltons on immunoblots of crude membrane proteins isolated from normal mouse brain but not from other tissues. Using a transient cotransfection assay, we showed that a plasmid construct expressing the Gβ5 open reading frame, when coexpressed with different G-protein y (Gy)-subunits, can stimulate the activity of the β2 isoform of phosphoinositide-specific phospholipase C (PLCβ2). The stimulation of PLCβ2 was most pronounced when Gβ5 was co-expressed with Gy2, although activation was observed when Gβ5 was cotransfected with either Gy1, Gy3, Gy5, or Gy_(cone). These results prove that Gβ5 can functionally associate with Gy proteins and is therefore a bona fide member of the Gβ protein family. The rather low level of identity between Gβ5 and the other mammalian Gβ-subunits may shed light on structural/sequence elements necessary for Gβ protein function.

Additional Information

© 1994 American Society for Biochemistry and Molecular Biology. Received for publication, November 30, 1993, and in revised form, June 6, 1994. This research was supported by National Institutes of General Medical Sciences Fellowship GM13530 (to A. J. W.) and grants from the National Institutes of Health (to M. I. S.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The nucleotide sequence(s) reported in this paper has been submitted to the GenBank TM/EMBL Data Bank with accession number(s) L34290. We thank Drs. Bernard Fung and Jeannie Chen for cDNAs, Nancy Chen for performing the automated sequencing, and Dr. Thomas Wilkie for helpful comments on the manuscript.

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August 20, 2023
August 20, 2023