Phosducin and beta gamma-transducin interaction .1. Effects of post-translational modifications

The interaction between phosducin and beta gamma-transducin plays regulatory roles in light adaptation of photoreceptors. Both phosducin and beta gamma-transducin undergo post-translational modifications, with phosducin modified by phosphorylation and the gamma subunit of beta gamma-transducin by farnesylation and carboxylmethylation. In this study we exploited the electrophoretic mobilities of these native proteins to develop a micro binding assay and examined the effects of post-translational modifications on binding affinities. It was found that decarboxylmethylation of gamma-transducin increased the mobility of beta gamma-transducin during native gel electrophoresis, but decreased the apparent affinity for phosducin by about 2-fold, Phosphorylation of phosducin by protein kinase A increased the mobility but decreased the apparent affinity for beta gamma-transducin by at least 3-fold. (C) 1997 Academic Press.