Worm Breeder's Gazette 11(2): 32
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
G proteins play a central role in the response of cells and organisms to their environment by coupling cell surface receptors to intracellular 'effector' proteins. They are composed of three subunits: alpha, , and gamma. In most cells it is the alpha subunit that interacts with effectors. We are interested in using molecular genetic techniques to investigate the role of Galpha proteins in developmental processes and the function of the nervous system. Polymerase chain reaction (PCR) technology was used to isolate the fragments of 3 putative Galpha genes. Their predicted amino acid sequences are significantly similar to that of other Galpha proteins. In a region of 51 amino acids the sequences of PCR clones 2 and 3 are 88% identical to each other and are most closely related to the mammalian Gialpha (inhibitory Galpha protein) and GOalpha (the 'other' Ga protein) proteins. Over the same region the amino acid sequence of PCR clone 1 is only about 50% identical to that of PCR clones 2 or 3 and does not appear to be analogous to any known Galpha protein. Sequences of clones 1 and 3 available beyond that shown below indicate they are distinct from the Gsalpha (stimulatory Galpha protein) sequence reported by Ohshima, et al. (WBG 11(1), pg.33). We are currently isolating cDNA clones corresponding to these PCR-derived clones in order to define more precisely their relationship to each other and to G proteins found in other organisms. Cosmid clones PS#25A12, PS#01C2, and PS#14A3 corresponding to PCR clones 1, 2, and 3 respectively have been isolated from a WEKan library (see description in this issue) and mapped by Alan Coulson et al. All three cosmids map to dispersed locations in the cluster of chromosome five. A fourth cosmid, PS#74B3, was isolated that weakly hybridizes to PCR clone 1 and maps to the right arm of the X chromosome. Its identity is unknown and is under investigation. A 1.5 kbp cDNA clone was isolated by low stringency hybridization to a mixture of the three PCR- derived clones. The nucleotide sequence of the insert was determined and an open reading frame of 354 amino acids was found that encodes a protein homologous to GOalpha. The amino acid sequence of C. elegans GOalphha is about 80% identical to mammalian or Drosophila GOalpha and is clearly different from the PCR clones described above. We are currently analyzing several presumtive GOalpha genomic clones isolated from our WEKan library. In mammals GOalpha has been implicated in coupling neurotransmitter receptors to the activation of Ca2+ and K+ channels. It is particularly abundant in brain and is found only in organisms with nervous systems (i.e. not yeast or slime mold). Over 15 different G proteins have been found in mammals. C. elegans probably has at least 5 G proteins. Two of these are identifiable homologs of mammalian G proteins. Therefore C. elegans may serve as a useful system for studying G proteins by means that would be difficult in more complex organisms.