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Updated: Aug 14, 2026

Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
Published on: May 26, 2011
Sites of interaction in the complex between beta- and gamma-subunits of transducin
1Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Abstract:
Transducin, the guanine nucleotide-binding regulatory protein in rod outer segments, is a heterotrimer consisting of alpha-, beta-, and gamma-subunits. Activation of the photoreceptor, rhodopsin, by light, results in activation of transducin which cleaves to form transducin alpha. GTP and a complex of beta gamma-subunits. We have investigated the point(s) of contact between the subunits of transducin by analyzing for the formation of intersubunit disulfide bond(s) in the presence of copper phenanthroline. The formation of a new species with an apparent molecular mass of 43 kDa was observed which had resulted from the formation of a disulfide bond between the beta- and gamma-subunits. The amino acid residues participating in the disulfide bond were identified as Cys-25 in the beta-subunit and Cys-36 and/or Cys-37 in the gamma-subunit. Thus, these cysteine residues and, probably, some of the adjacent amino acid residues form a point of contact between the beta- and gamma-subunits of transducin in the stable complex.
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