Oxygen-evolving complex polypeptides

Simpson, D.J. and Andersson B. 1986. Extrinsic polypeptides of the chloroplast oxygen evolving complex constitute the tetrameric ESs particles of higher plant thylakoids. Carlsberg Res. Commun. 51,467-474. 

The three extrinsic 33 kDa, 24 kDa and 18 kDa polypeptides of the oxygen-evolving complex are associated with the PS II complex at the lumenal side of the membrane [34,35] (Fig. 1). Each of the three proteins is able to re-bind stoichiomet-rically to depleted PS II complexes. The 33 and 24 kDa proteins bind directly to the complex, with the 33 kDa protein promoting binding of the 24 kDa protein [34,36], while the 18 kDa protein binds to the 24 kDa protein only when the latter polypeptide is bound to the PS II complex [37]. The 33 and 24 kDa proteins appear to be directly associated with two uncharacterized polypeptides of 24 kDa and 10 kDa that are also present in the PS II complex [36]. 

JG Metz, PJ Nixon, M R gner, GW Brudvig and BA Diner (1989) Directed alteration of the D1 polypeptide of photosystem II Evidence that tyrosine-161 is the redox component, Z, connecting the oxygen-evolving complex to the primary electron donor, P680. Biochemistry 28 6960-6969... 

S2, S3, and S4. S is the most reduced state and S4 is the most oxidized state of the complex. It is now believed that the Mn cluster, a group of four manganese atoms bound to MSP near the PSII reaction center, is mostly responsible for these transitions. As the oxygen-evolving complex abstracts electrons and protons from HzO, it cycles through the five oxidation states. The electrons are transferred one at a time to a tyrosine residue on the Dj polypeptide and then to the P680 reaction center. The protons released in the process remain in the thylakoid lumen, where they contribute to the pH gradient that drives ATP synthesis. 

Wales R, Newman BJ, Pappin D et al. The extrinsic 33 kDa polypeptide of the oxygen-evolving complex of photosystem II is a putative calcium-binding protein and is encoded by a multigene family in pea. Plant Mol Biol 1989 12 439-451. 

The distribution of tm for 6 = 170 (P) and 8 = 100 (ot) is shown in Fig. 1 for selected members of the families of chloroplastic precursors. The amino acid sequences of the transit peptides are shown in the bottom panel. The plots are aligned according to the cleavage site at the end of the transit peptide. Proteins destined for the thyla-koid lumen (i.e., plastocyanin and the polypeptides of the oxygen evolving complex) must traverse the thylakoid membrane in addition to the envelope membranes. For these precursors, the first 40-60 amino acids comprise the stromal targeting domain, whereas the last 20-25 residues form the thylakoid transport domain (9). Thus, it is the first domain that is relevant for comparison with the other transit peptides. 

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