STRUCTURAL CONSEQUENCES OF AMMONIA BINDING TO THE MANGANESE CENTER OF THE PHOTOSYNTHETIC OXYGEN-EVOLVING COMPLEX - AN X-RAY-ABSORPTION SPECTROSCOPY STUDY OF ISOTROPIC AND ORIENTED PHOTOSYSTEM-II PARTICLES

被引：110

作者：

DAU, H

ANDREWS, JC

ROELOFS, TA

LATIMER, MJ

LIANG, WC

YACHANDRA, VK

SAUER, K

KLEIN, MP

机构：

[1] UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,DIV STRUCT BIOL,BERKELEY,CA 94720

[2] UNIV CALIF BERKELEY,DEPT CHEM,BERKELEY,CA 94720

来源：

BIOCHEMISTRY | 1995年 / 34卷 / 15期

关键词：

D O I：

10.1021/bi00015a043

中图分类号：

Q5 [生物化学]; Q7 [分子生物学];

学科分类号：

071010 ; 081704 ;

摘要：

The structure and orientation of the manganese complex in NH3-treated photosystem II (PS II) membrane particles of spinach are being studied by X-ray absorption spectroscopy. On the basis of earlier work by our group, a structure for the tetranuclear manganese complex of PS II, which consists of two di-mu-oxo-bridged binuclear Mn units linked by a mono-mu-oxo group, has been proposed [Yachandra, V. K., et al. (1993) Science 260, 675-679]. The extended X-ray absorption fine structure (EXAFS) of the complex modified by NH3 binding in the S-2-state is suggestive of an increase in the Mn-Mn distance of one of these units from 2.72 +/- 0.02 to 2.87 +/- 0.02 Angstrom, whereas the Mn-Mn distance of the second unit seems to be unaffected by NH3 treatment. The elongation of one binuclear center could result from the replacement of one bridging mu-oxo by an amido group. The lengthening of one Mn-Mn distance means that, by NH3 treatment, the distance degeneracy of the 2.7 Angstrom Mn-Mn EXAFS interaction is removed. Consequently, the orientation of individual binuclear units with respect to the membrane normal becomes resolvable by EXAFS spectroscopy of partially oriented PS II membrane particles. The angle between the normal of the PS II-containing membrane and the Mn-Mn vector is determined to be 67 degrees +/- 3 degrees for the 2.87 Angstrom distance and 55 degrees +/- 4 degrees for the 2.72 Angstrom distance. Only small effects on position, shape, and orientation dependence of Mn K-edge spectra result from NH3 treatment, indicating that the Mn oxidation state, the symmetry of the Mn ligand environment, and the orientation of the complex remain essentially unaffected in the annealed NH3 S-2-state. Therefore, it seems likely that the angles determined for the ammonia-modified manganese complex are similar to the respective angles of the untreated complex. The structure of the manganese complex and its orientation in the membrane are discussed.

引用

页码：5274 / 5287

页数：14

共 57 条

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