Molecular cloning and sequence determination of a cDNA coding for the α‐subunit of a Go‐type protein of Xenopus laevis oocytes

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Abstract
Xenopus laevis oocytes are cells ideally suited to the study of signal transduction and of the G‐proteins that are involved in this process. A X. laevis cDNA library in λgt10 has been screened with a mixture of three oligonucleotide probes designed to detect sequences found in various mammalian α‐subunits of G‐proteins. One of these clones has been purified through tertiary screening and the DNA insert has been sequenced. This clone was found to include the total sequence coding for a 354 amino acid protein that is 89% identical to the sequence of α‐subunit of rat Go. The differences with the mammalian protein were clustered in amino acids 290–315, which have been postulated to define the region interacting with the receptor and effector molecule. The homology with the α‐subunits of other mammalian G‐proteins is lower (65–70% to Gi and 42% to Gs). On this basis, this clone can be classified as Go‐like.