| Abstract
| - Photosystem II reaction centers (RC) isolated from peas(Pisum sativum L) purified by ion-exchange chromatography were shown, by high-performance liquidchromatography (HPLC) size-exclusionanalyses, to consist of a mixture of monomers (180 ± 20 kDa) anddimers (390 ± 35 kDa). Both fractionswere resolved and purified by sucrose density gradient centrifugationand their homogeneity wasdemonstrated in size-exclusion HPLC elution profiles. Also presentin the nonresolved preparation andthe monomeric fraction were low levels of CP47 apoprotein (1.8% and0.9% apoprotein of that found ina CP47-RC preparation). This CP47 contamination could maximallyaccount for 0.41 and 0.22 Chl/RC,respectively, based on 22 chlorophylls being bound to each CP47protein. The level of CP47 apoproteinwas undetectable in the dimeric fractions. Pigment analysis usingreverse-phase HPLC confirmed thatcontamination by chlorophyll bound to the CP47 apoprotein in thenonresolved RC preparation was lowand that the ratio of chlorophyll a to pheophytina remained 6 when the preparation was separatedintoits monomeric and dimeric components. We conclude, in agreementwith earlier work, that the reactioncenter of PSII, when isolated using mild detergents and ion-exchangechromatography, contains 6chlorophyll a/2 pheophytin a. We thereforedo not concur with the recent published work of Pueyo etal.[(1995) Biochemistry 34, 15214−15218) that this type ofpreparation contains 4 chlorophyll a/2pheophytina and that the remaining 2 chlorophyll a are dueto contamination by CP47.
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