Proteomic Analysis of a Highly Active Photosystem II Preparation from the Cyanobacterium Synechocystis sp. PCC 6803 Reveals the Presence of Novel Polypeptides

摘要

A highly active oxygen-evolving phoptosystem II (PSII) complex was purified from the HT-3 strain of the widely used cyanbobacterium Synechocystis sp. PCCC 6803, in which the CP47 polypeptide has been genetically engineered to contain a polyhistidine tag at its carboxyl termins [Bricker, T.M., Morvant, J., Masri, N., Sutton, H.M., and Frankel, L.K. (1998) Biochim. Biophys. Acta 1409, 50-57]. These purified PSII centers and four manganese atoms, one calcium atom, and two cytochrome b_559 hemes each. Optical absorption and fluorescence emission spectroscopy as well as western immunoblot analysis demonstrated that the purified PSII preparation was devoid of any contamination with photosystem I and phycobiliproteins. A comprehensive proteomic analysis using a system designed to enhanced resolution of low-molecular-weight polypeptides, following by MALDI mass spectrometry and N-terminal amino acid sequencing, identified 31 distinct polypeptides in this PSII preparation. We propoe a new nomenclature for the polypeptide components of PSII identified after PsbZ, which proceeds sequentially from Psb27. During this study, the polypeptides PsbJ, PsbM, PsbX, PsbZ, Psb27, and Psb28 proteins were detected for the first time in a purified PSII complex from Synechocytis 6803. Five novel polypeptides were also identified in this preparation. They included the SII 1638 protein, which shares significant sequence similarity to PsbQ, a peripheral protein off PSII that was previously thought to be present only in chloproplasts. This work describes newly identified proteins in a highl puriifed cyanobacterial PSII preparation that is being widely used to investigate the structure, function, and biogensis of this photosystem.