The detection and characterization of G‐proteins in the eyespot of Chlamydomonas reinhardtii

Abstract
The presence of G‐proteins in the eyespot fraction of Chlamydomonas reinhardtii is shown. This fraction is capable of binding (GTPγ[35S], possesses the GTPase activity and interacts with antibodies raised against a highly conserved peptide of most G‐proteins' α‐subunit. Cross‐reaction with a 24‐kDa protein is detected on immunoblots. Using an antiserum prepared from vertebrate β‐subunit peptide, two additional proteins with apparent M r 21 and 29 kDa could be revealed. The light‐dependence of GTPase extraction from eyespot membranes is shown. The results make it possible to suggest the participation of G‐proteins in the photosensory transduction chain of Ch. reinhardtii.