On the role of water‐soluble polypeptides (17, 23 kDa), calcium and chloride in photosynthetic oxygen evolution

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116934/1/feb20014579385800302.pd

Calcium reconstitutes high rates of oxygen evolution in polypeptide depleted Photosystem II preparations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116911/1/feb20014579384808467.pd

Water‐soluble 17 and 23 kDa polypeptides restore oxygen evolution activity by creating a high‐affinity binding site for Ca2+ on the oxidizing side of Photosystem II

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117036/1/feb20014579384813939.pd

Comparative structural and catalytic properties of oxygen-evolving photosystem II preparations

Biochemical techniques now exist to produce the oxygen-evolving complex of photosystem II (PSII) and its associated photochemical redox reactions in various states of purity. These preparations permit one to assess the structural roles of polypeptides in promoting activity by using selective extraction techniques which remove certain polypeptides, to carry out reconstitution studies which re-establish activity, and, in the case of more recently developed, highly purified preparations discussed in this overview, to identify the minimal polypeptide complement necessary for photosynthetic oxygen evolution activity. These comparative investigations also suggest a tentative structure for an oxygen-evolving PSII core complex whose primary constituents are a hydrophobic complex of polypeptide, manganese, calcium and chloride, and the 33 kDa extrinsic polypeptide.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43533/1/11120_2004_Article_BF00032704.pd

Mn 2+ reduces Y z + in manganese-depleted Photosystem II preparations

Manganese in the oxygen-evolving complex is a physiological electron donor to Photosystem II. PS II depleted of manganese may oxidize exogenous reductants including benzidine and Mn 2+ . Using flash photolysis with electron spin resonance detection, we examined the room-temperature reaction kinetics of these reductants with Y z + , the tyrosine radical formed in PS II membranes under illumination. Kinetics were measured with membranes that did or did not contain the 33 kDa extrinsic polypeptide of PS II, whose presence had no effect on the reaction kinetics with either reductant. The rate of Y z + reduction by benzidine was a linear function of benzidine concentration. The rate of Y z + reduction by Mn 2+ at pH 6 increased linearly at low Mn 2+ concentrations and reached a maximum at the Mn 2+ concentrations equal to several times the reaction center concentration. The rate was inhibited by K + , Ca 2+ and Mg 2+ . These data are described by a model in which negative charge on the membrane causes a local increase in the cation concentration. The rate of Y z + reduction at pH 7.5 was biphasic with a fast 400 μs phase that suggests binding of Mn 2+ near Y z + at a site that may be one of the native manganese binding sites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43534/1/11120_2004_Article_BF00048306.pd