The phosphorylation state of transducin beta-subunits
Orlov, D.N.; Nezvetskiĭ, A.R.; Orlova, T.G.; Petrukhin, O.V.; Orlov, N.I.
Biofizika 59(5): 837-842
2015
ISSN/ISBN: 0006-3029 PMID: 25730960 Document Number: 682088
The supposition that nucleoside diphosphate kinase is the enzyme that phosphorylates transducin beta-subunits on one of the histidine residues (His-266) has been analyzed. It stands the reason that 1) this enzyme is multifunctional and plays in particular the role of protein histidine kinase; and 2) the phosphorylated beta-subunit of transducin may activate transducin via the mechanism of transphosphorylation. Nevertheless, in our experiments, in which different forms of transducin preparations were incubated with α- and β-isoforms of recombinant rat NDP kinase in the presence of [γ32P]ATP or [γ32P]GTP (specific activity of about 1 Ci/mmol) followed by separation of proteins by electrophoresis and-gel radio-autography, the phosphorylation of the transducin beta-subunit wasn't succeeded to be found. The negative result of our experiments most likely implies that the major part of transducin beta-subunits in the preparations has already been phosphorylated via a process that takes place in vivo.