Cone Photoreceptor -Transducin: Posttranslational Modification and Interaction with Phosducin

RESULTS. The mature T 8 is a 65-amino-acid peptide encoded by the G 8 gene with an acetylated and a farnesylated–methylated Nand C-terminus, respectively. Purified T 3 8 is similar to T 1 1 in that (1) both are heterogeneous, containing methylated and demethylated T subunits; (2) each demethylated dimer migrates faster than its methylated counterpart during native gel electrophoresis, and the methylation-associated mobility differential is masked by pdc binding; and (3) both dimers bind pdc with the same affinity, and the affinity is reduced threefold by PKA phosphorylation of pdc and twofold by demethylation at the C-terminus of T . T 3 8 differs from T 1 1 in exhibiting lower intrinsic electrophoretic mobility, and the difference is unaffected by either pdc binding or the status of T methylation.