Photosystem I core

Abstract

Recent work on the structure of photosystem I (PS I) is reviewed in historical context. Composition and methods of preparation of the reaction center, core and antennae are described. Emphasis is on the polypeptide composition of the various parts of the photosystem, especially the core, which also includes the reaction center. Recent work on the assignment of iron-sulfur centers to particular polypeptides is described as well as work on other early electron acceptors. The interactions of PS I with ferredoxin (which forms the link to pyridine nucleotide reduction) and with plastocyanin (which forms the link with the cytochrome b 6/f complex) are presented. Reports on the sequences of chloroplast- and nuclear-coded polypeptide components of PS I are summarized along with interpretations of the structure of the photosystem derived from such results. Work on attempts to determine structure at the atomic level by X-ray crystallography is described. The relationship of green plant and cyanobacterial PS I to various types of bacterial photosynthetic pigment-protein complexes is discussed. The protein-dimer nature of PS I reaction center is reviewed and evaluated. Data suggesting that the isolated green plant PS I reaction center may not be a protein-dimer are presented.