Carboxylate Groups on the Manganese-Stabilizing Protein Are Required for Efficient Binding of the 24 kDa Extrinsic Protein to Photosystem II†

Terry M. Bricker, Laurie K. Frankel
2003 Biochemistry  
The effects of the modification of carboxylate groups on the manganese-stabilizing protein on the binding of the 24 kDa extrinsic protein to Photosystem II were investigated. Carboxylate groups on the manganese-stabilizing protein were modified with glycine methyl ester in a reaction facilitated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The manganese-stabilizing protein which was modified while associated with NaCl-washed membranes could bind to calcium chloride-washed PS II membranes
more » ... d reconstitute oxygen evolution in a manner similar to that observed for unmodified manganese-stabilizing protein (Frankel, L.K, Cruz, J. C. and Bricker, T. M. (1999) Biochemistry 38, 14271-14278). However, PS II membranes reconstituted with this modified protein were defective in their ability to bind the extrinsic 24 kDa protein of Photosystem II. Mapping of the sites of modification was carried out by trypsin and Staphylococcus V8 protease digestion of the modified protein and analysis by MALDI mass spectrometry. These studies indicated that the domains 1 E-71 D, 97 D-144 D, and 180 D-187 E are labeled when the manganesestabilizing protein is bound to NaCl-washed Photosystem II membranes. We hypothesize that modified carboxylates, possibly residues 1 E, 32 E, 139 E, and/or 187 E, in these domains are responsible for the altered binding affinity of the 24 kDa protein observed.
doi:10.1021/bi020652v pmid:12590593 fatcat:7flczy7xvnghlbxqumidej7in4