Cone photoreceptor betagamma-transducin: posttranslational modification and interaction with phosducin.

Purpose: To characterize the structure of cone betagamma-transducin (Tbeta3gamma8) and its interaction with phosducin (pdc).

Methods: The Tgamma8 subunit of Tbeta3gamma8 was isolated by column chromatography for peptide mapping with mass spectrometry. Tbeta3gamma8 was compared with rod betagamma-transducin (Tbeta1gamma1) in terms of the electrophoretic mobility, pdc binding affinity, and the effects of phosphorylation and methylation, and then the correlation to the crystal structures and functional domains of Tbeta1gamma1 was determined.