Phosphorylation of the α and β polypeptides of the light-harvesting complex I (B870) of Rhodobacter capsulatus in an in vitro translation system

Abstract

Synthesis and phosphorylation of the proteins α and β of the light-harvesting (LH) complex I (B870) were investigated in a cell-free translation system of Rhodobacter capsulatus. Both proteins were incorporated into the membrane fraction; LHIβ was inserted in the absence of LHIα was phosphorylated in the presence of [γ-32P]ATP only when membranes were present. Phosphorylated LHIβ was found only in the absence of membranes. The phosphate group bound to LHIβ was not transferred to LHIα during insertion. The results indicate that a membrane-bound and a soluble protein kinase are involved. Strong light reduced the amount of phosphorylated LHIα. The results are discussed with respect to the assembly and function of LHI. © 1994.