Isolation and Comparison of Molecular Properties of Cytochrome £-559 from Both Spinach Thylakoids and PS II Particles

Abstract

Abstract Cytochrome b-559. Spinach Thylakoids. PS II Particles. High and Low Potential. Interconvertible Forms Cytochrome b-559 has been purified from both spinach (Spinacia oleracea L.) thylakoids and photosystem II particles in order to compare some of its more polemic molecular properties. In the two cases, cytochrome 6-559 (which is initially present in its reduced high-potential form and in its oxidized low-potential form) is purified as a single species by preparative disc electrophoresis in Triton-containing polyacrylamide gel, the isolated protein exhibiting similar molecular mass and almost identical low midpoint redox potential and absorption spectra. Moreover, sodium dodecyl sulfate polyacrylamide gel electrophoresis of the purified cytochrom e b-559 reveals, again in both cases, only one polypeptide band of similar molecular mass. Integration o f the isolated low-potential form into liposomes partly restores the high-potential form. These data corroborate our previous results and indicate that there exists in thylakoids only a cytochrome b -559 molecular species tightly bound to PS II and that the two naturally occurring low-and high-potential couples are physiological and correspond to interconvertible states of the genuine hem e protein.