Structural comparison of oxygen-evolving photosystem II core complexes from Synechococcus elongatus and Spinacia oleracea

Abstract

The molecular composition of oxygen evolving ß-n-dodecylmaltoside-solubilised PS II core complexes from Synechococcus elongatus and Spinacia oleracea have been structurally analysed by SDS/urea/PAGE, immunoblotting using monospecific antibodies directed against PS II polypeptides, MALDI-TOF-MS and absorbance difference spectroscopy. A detailed cofactor analysis was likewise carried out. According to our investigations PS II core complexes from the cyanobacterium consist of at least 17 different proteins and that of spinach of s 15 subunits. One copy of cytb559 and cyt c550 were identified per cyanobacterial PS II complex. In contrast to spinach PS II core complexes no phosphorylated protein could be identified in the cyanobacterial PS II by phosphoamino acid specific antibodies (a-P-Thr, -P-Ser and -P-Tyr). In addition we addressed the question under which experimental conditions PS II core complexes of both sources occur as monomers or dimers by gel permeation HPLC, static/ dynamic light scattering and analytical ultracentrifugation. The results will be discussed in the light of recent structural models for PS II.