The Unfinished Story of Cytochrome f

Cytochrome f is a unique, integral membrane protein. The background to its discovery by Robert Hill (1899-1991) and Ronald Scarisbrick over 60 years ago and the influence of David Keilin (1887-1963) and Frederick Gowland Hopkins (1861-1947) are discussed. The development of methods for isolating cytochrome f is outlined, emphasizing the remarkable achievement of Hill and Scarisbrick at a time when few if any membrane proteins had been isolated, and the importance of the discovery of a natural proteolysis in Brassica spp., stimulated by organic solvents, by Eijiro Yakushiji and coworkers and by Masa-aki Takahashi and Kozi Asada in 1975. The significance of different types of instrumentation in the study of cytochrome f is discussed, drawing attention to the importance of the microspectroscope ocular for its discovery, to types of spectrophotometer developed especially by Britton Chance for spectrophotometric measurements on turbid suspensions of cells and plastids, and to the history of stopped-flow spectrophotometry. The stopped-flow instrument originated in the bucket-scale flow methods of Hartridge and Roughton (1923), and was later developed on the microscale by Chance. Finally, the problems that remain for understanding the behavior of cytochrome f in the thylakoid lumen are contrasted with the significance of in vitro studies that provide a paradigm for transient protein-protein interactions in the wider field of biology as a whole.