Abstract
The 33-kDa manganese-stabilizing protein stabilizes the manganese cluster in the oxygen-evolving complex. There has been, however, a considerable amount of controversy concerning the stoichiometry of this photosystem II (PS II) component. In this paper, we have verified the extinction coefficient of the manganese-stabilizing protein by amino acid analysis, determined the manganese content of oxygen-evolving photosystem II membranes and reaction center complex using inductively coupled plasma spectrometry, and determined immunologically the amount of the manganese-stabilizing protein associated with photosystem II. Oxygen-evolving photosystem II membranes and reaction center complex preparations contained 258 +/- 11 and 67 +/- 3 chlorophyll, respectively, per tetranuclear manganese cluster. Immunoquantification of the manganese-stabilizing protein using mouse polyclonal antibodies on "Western blots" demonstrated the presence of 2.1 +/- 0.2 and 2.0 +/- 0.3 molecules of the manganese-stabilizing protein/tetranuclear manganese cluster in oxygen-evolving PS II membranes and highly purified PS II reaction center complex, respectively. Since the manganese-stabilizing protein co-migrated with the D2 protein in our electrophoretic system, accurate immunoquantification required the inclusion of CaCl2-washed PS II membrane proteins or reaction center complex proteins in the manganese-stabilizing protein standards to compensate for the possible masking effect of the D2 protein on the binding of the manganese-stabilizing protein to Immobilon-P membranes. Failure to include these additional protein components in the manganese-stabilizing protein standards leads to a marked underestimation of the amount of the manganese-stabilizing protein associated with these photosystem II preparations.
Highlights
The 33-kDamanganese-stabilizingproteinstabilizes D2 proteins, thea and p (9 and4.5 kDa, respectively) subunits the manganese clusterin thoexygen-evolving complex. of cytochrome b559C, Pa-1 (CP47), CPa-2 (CP43), and t4h.8e
Pm0and Z, and the electron acceptors pheophytin aQ, A,and QB (Nanba and Satoh, 1987; Deisenhofer et al, 1985; Ghanotakis et al, 1989). It appears to provide ligands for the don o r s, Oxygen-evolving photosystem I1 membranes and re- tetrameric manganese clusterwhich accumulates the oxidizaction center complex preparations contained 258 f ing equivalents required for water oxidation (Tamura et al, 11 and 67 f 3 chlorophyll, respectively, per tetranu- 1989; Seibert e t al., 1989)
The extrinsic 17- and24-kDa proteins, antibodies on “Western blots” demonstrated the pres- which are absent in the cyanobacteria (Stewart et al, 1985), ence of 2.1 f 0.2 and 2.0 f 0.3 molecules of the man- optimize oxygen evolution in higher plants by regulating ganese-stabilizinPgroteinJtetranuclemaranganese calcium and chloride levels inthe vicinity of thewaterclusterin oxygen-evolving PS I1 membranes and oxidizing site (Ghanotakis and Yocum, 1990)
Summary
The 33-kDamanganese-stabilizingproteinstabilizes D2 proteins, thea and p (9 and4.5 kDa, respectively) subunits the manganese clusterin thoexygen-evolving complex. of cytochrome b559C, Pa-1 (CP47), CPa-2 (CP43), and t4h.8e-. The oxygenevolving PS I1 membranes contained intrinsic proteins with apparent molecularmasses of 52 (CPa-l), 44 (CPa-2), 34 more than 99% of the manganese-stabilizing protein from oxygen- (D2), 32 (Dl), 26-29 (LHC 11), and 9kDa ( a subunit of evolving P S I1 membranes (Bricker, 1992) and reaction center complex.'
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
