Evidence that CP 47 (CPa-1) is the Reaction Centre of Photosystem II

Summary

Two lines of evidence support the identification of the chlorophyll a-protein complex CPa-1 (CP 47) as the reaction centre core complex of Photosystem II (PS II). When PS II core particles are prepared by octyl glucoside extraction and sucrose gradient sedimentation, maximum PS II activity (DPC → DCPIP) coincides with the peak of CPa-1, and does not coincide with that of any other chlorophyll-protein complex. Secondly, the complex CPa-1 is the only complex missing from the corn mutant hcf*-3, which is totally lacking in PS II activity.

We propose that the other chlorophyll-protein complex associated with reaction centre preparations, CPa-2 (CP 43) may be an internal antenna complex. A model is presented suggesting a possible organization of these complexes in the core of PS II, associated with the minor Chi a+b complex CP 29 and a variable number of units of the light-harvesting complex (LHCP).