THE 23 AND 17 KDA EXTRINSIC PROTEINS OF PHOTOSYSTEM-II MODULATE THE MAGNETIC-PROPERTIES OF THE S-1-STATE MANGANESE CLUSTER

An S-1-state parallel polarization ''multiline'' EPR signal arising fr om the oxygen-evolving complex has been detected in spinach (PSII) mem brane and core preparations depleted of the 23 and 17 kDa extrinsic po lypeptides, but retaining the 33 kDa extrinsic protein. This S-1-state multiline signal, with an effective g value of 12 and at least 18 hyp erfine Lines, has previously been detected only in PSII preparations f rom the cyanobacterium sp. Synechocystis sp. PCC6803 [Campbell, K. A., Peloquin, J. M., Pham, D. P., Debus, R. J., and Britt, R. D. (1998) J . Am. Chem. Sec. 120, 447-448]. It is absent in PSII spinach membrane and core preparations that either fully retain or completely lack the 33, 23, and 17 kDa extrinsic proteins. The S-1-state multiline signal detected in spinach PSII cores and membranes has the same effective g value and hyperfine spacing as the signal detected in Synechocystis PS II particles. This signal provides direct evidence for the influence o f the extrinsic PSII proteins on the magnetic properties of the Mn clu ster.