Influence of the 33 kDa Manganese-Stabilizing Protein on the Structure and Substrate Accessibility of the Oxygen-Evolving Complex of Photosystem II

详细信息    查看全文

• 作者：Wolfgang Gregor ; Roehl M. Cinco ; Hui Yu ; Vittal K. Yachandra ; and R. David Britt
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：June 21, 2005
• 年：2005
• 卷：44
• 期：24
• 页码：8817 - 8825
• 全文大小：196K
• 年卷期：v.44,no.24(June 21, 2005)
• ISSN：1520-4995

文摘

The 33 kDa manganese-stabilizing extrinsic protein binds to the lumenal side of photosystemII (PS II) close to the Mn₄Ca cluster of the oxygen-evolving complex, where it limits access of smallmolecules to the metal site. Our previous finding that the removal of this protein did not alter the magneticcoupling regime within the manganese cluster, measured by electron spin-echo envelope modulation[Gregor, W., and Britt, R. D. (2000) Photosynth. Res. 65, 175-185], prompted us to examine whetherthis accessibility control is also true for substrate water, using the same pulsed EPR technique. Comparingthe deuteron modulation of the S₂-state multiline signal of PS II membranes, equilibrated with deuteratedwater (D₂O) after removal or retention of the 33 kDa protein, we observed no change in the number andthe distance of deuterons magnetically coupled to manganese, indicating that the number and distance ofwater molecules bound to the manganese cluster are independent of bound 33 kDa protein in the S₁ state,in which the sample was poised prior to cryogenic illumination. A simple modulation depth analysisrevealed a distance of 2.5-2.6 Å between the closest deuteron and manganese. These results are inagreement with our refined X-ray absorption analysis. The manganese K-edge positions, reflecting theiroxidation states, and the extended X-ray absorption fine structure amplitudes and distances between themanganese ions and their oxygen and nitrogen ligands (1.8, 2.7, and 3.3-3.4 Å) were independent ofbound 33 kDa protein.