Study of Interactions between Huge Membrane Proteins and Soluble Proteins
—Application to Photosynthetic Proteins—

Abstract

In the photosynthetic light reactions of plants and cyanobacteria, plastocyanin plays a crucial role as an electron carrier and shuttle protein between two membrane protein complexes: cytochrome b₆f and photosystem I. Using transferred cross-saturation method, we demonstrated that the hydrophobic patch residues of plastocyanin are in close proximity to PSI and cytochrome b₆f, whereas the acidic patch residues of plastocyanin do not form stable salt bridges with either PSI or cyt b₆f, in the electron transfer complexes. The transient characteristics of the interactions on the acidic patch facilitate the rapid association and dissociation of plastocyanin.