Debus R J, Campbell K A, Gregor W, Li Z L, Burnap R L, Britt R D
Department of Biochemistry, University of California, Riverside, California 92521-0129, USA.
Biochemistry. 2001 Mar 27;40(12):3690-9. doi: 10.1021/bi002394c.
The tetranuclear manganese cluster in photosystem II is ligated by one or more histidine residues, as shown by an electron spin echo envelope modulation (ESEEM) study conducted with [(15)N]histidine-labeled photosystem II particles isolated from the cyanobacterium Synechocystis sp. strain PCC 6803 [Tang, X.-S., Diner, B. A., Larsen, B. S., Gilchrist, M. L., Jr., Lorigan, G. A., and Britt, R. D. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 704-708]. One of these residues may be His332 of the D1 polypeptide. Photosystem II particles isolated from the Synechocystis mutant D1-H332E exhibit an altered S(2) state multiline EPR signal that has more hyperfine lines and narrower splittings than the corresponding signal in wild-type PSII particles [Debus, R. J., Campbell, K. A., Peloquin, J. M., Pham, D. P., and Britt, R. D. (2000) Biochemistry 39, 470-478]. These D1-H332E PSII particles are also unable to advance beyond an altered S(2)Y(Z)() state, and the quantum yield for forming the S(2) state is very low, corresponding to an 8000-fold slowing of the rate of Mn oxidation by Y(Z)(). These observations are consistent with His332 being close to the Mn cluster and modulating the redox properties of both the Mn cluster and tyrosine Y(Z). To determine if D1-His332 ligates the Mn cluster, we have conducted an ESEEM study of D1-H332E PSII particles. The histidyl nitrogen modulation observed near 5 MHz in ESEEM spectra of the S(2) state multiline EPR signal of wild-type PSII particles is substantially diminished in D1-H332E PSII particles. This result is consistent with ligation of the Mn cluster by D1-His332. However, alternate explanations are possible. These are presented and discussed.
光系统II中的四核锰簇由一个或多个组氨酸残基连接，这是通过对从集胞藻属PCC 6803蓝细菌中分离出的[(15)N]组氨酸标记的光系统II颗粒进行电子自旋回波包络调制（ESEEM）研究得出的[Tang, X.-S., Diner, B. A., Larsen, B. S., Gilchrist, M. L., Jr., Lorigan, G. A., and Britt, R. D. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 704 - 708]。这些残基之一可能是D1多肽的His332。从集胞藻突变体D1 - H332E中分离出的光系统II颗粒表现出改变的S(2)态多线EPR信号，与野生型PSII颗粒中的相应信号相比，该信号具有更多的超精细线且分裂更窄[Debus, R. J., Campbell, K. A., Peloquin, J. M., Pham, D. P., and Britt, R. D. (2000) Biochemistry 39, 470 - 478]。这些D1 - H332E光系统II颗粒也无法超越改变的S(2)Y(Z)()态，并且形成S(2)态的量子产率非常低，这对应于Y(Z)()使锰氧化速率减慢8000倍。这些观察结果与His332靠近锰簇并调节锰簇和酪氨酸Y(Z)的氧化还原性质一致。为了确定D1 - His332是否连接锰簇，我们对D1 - H332E光系统II颗粒进行了ESEEM研究。在野生型PSII颗粒的S(2)态多线EPR信号的ESEEM光谱中，在5 MHz附近观察到的组氨酸氮调制在D1 - H332E光系统II颗粒中显著减弱。该结果与D1 - His332连接锰簇一致。然而，也可能有其他解释。本文将呈现并讨论这些解释。
