New Structural and Mechanistic Insights Into Functional Roles of Cytochrome b(559) in Photosystem II

Cytochrome (Cyt) b(559) is a key component of the photosystem II (PSII) complex for its assembly and proper function. Previous studies have suggested that Cytb(559) has functional roles in early assembly of PSII and in secondary electron transfer pathways that protect PSII against photoinhibition. In addition, the Cytb(559) in various PSII preparations exhibited multiple different redox potential forms. However, the precise functional roles of Cytb(559) in PSII remain unclear. Recent site-directed mutagenesis studies combined with functional genomics and biochemical analysis, as well as high-resolution x-ray crystallography and cryo-electron microscopy studies on native, inactive, and assembly intermediates of PSII have provided important new structural and mechanistic insights into the functional roles of Cytb(559). This mini-review gives an overview of new exciting results and their significance for understanding the structural and functional roles of Cytb(559) in PSII.