Molecular cloning of cdnas encoding human rgs5 and rgs13

RGS proteins comprise a family of proteins identified first as negative regulators of heterotrimeric dprotein signaling in S. cereyisiaeand C.'.elcgans. The existence of a semi-conserved sequence of approximately 120 amino acids in these proteins (RGS domain) facilitated the cDNA cloning and/or identification of genes predicted to encode approximately twenty mammalian RGS proteins. Functional studies documented the ability of several cloned mammalian RGS proteins to negatively regulate G protein signaling. At present, complete sequence information is available for only six human RGS proteins and RGS 13 has not been cloned from any species. To provide insight into the structurai diversity of human RGS proteins, we undertook studies to clone full-length ci) N As encoding RGS proteins identified currently only as EST sequences. We PC R amplified the entire coding region of human RGS5 and RGS 13 transcripts. Human RGS5 is 181 amino acids and is most homologous to human RGS4. RGS 13 is 159 amino acids, the smallest RGS protein yet described, and is most homologous to human RGSl. RT-PCR analyses showed exclusive expression of human RGS5 transcripts in peripheral tissues, in contrast to the exclusive expression of human RGS4 in brain, while human RGS 13 transcripts were de tected only in lung. Comparison of the RGS domains of these two new human RGS proteins to that of rat RGS4 reveals conservation of residues implicated in RGS4-G, interactions based upon recent crystal structure findings, suggesting that human RGS5 and RGS13 have necessary structural features to interact with G proteins (NUI HL41071, DK25295).