title: Multiple copies of the PsbQ protein in a cyanobacterial photosystem II assembly intermediate complex.
abstract: Photosystem II (PSII) undergoes frequent damage owing to the demanding electron transfer chemistry it performs. To sustain photosynthetic activity, damaged PSII undergoes a complex repair cycle consisting of many transient intermediate complexes. By purifying PSII from the cyanobacterium Synechocystis sp. PCC 6803 using a histidine-tag on the PsbQ protein, a lumenal extrinsic subunit, a novel PSII assembly intermediate was isolated in addition to the mature PSII complex. This new complex, which we refer to as PSII-Q4, contained four copies of the PsbQ protein per PSII monomer, instead of the expected one copy. In addition, PSII-Q4 lacked two other lumenal extrinsic proteins, PsbU and PsbV, which are present in the mature PSII complex. We suggest that PSII-Q4 is a late PSII assembly intermediate that is formed just before the binding of PsbU and PsbV, and we incorporate these results into an updated model of PSII assembly.
authors: Department of Biology, CB1137, Washington University, 1 Brookings Drive, St. Louis, MO, 63130, USA.
authors: Haijun
authors: H
authors: Liu
authors: Department of Biology, CB1137, Washington University, 1 Brookings Drive, St. Louis, MO, 63130, USA.|Department of Chemistry, Washington University, St. Louis, MO, 63130, USA.
authors: Daniel A
authors: DA
authors: Weisz
authors: Department of Biology, CB1137, Washington University, 1 Brookings Drive, St. Louis, MO, 63130, USA. pakrasi@wustl.edu.
authors: Himadri B
authors: HB
authors: Pakrasi
mesh_terms: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins / Q000378:metabolism; D006639:Histidine; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D046939:Synechocystis / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D045332:Photosystem II Protein Complex; C121497:psbQ protein, Arabidopsis; D006639:Histidine; D010100:Oxygen
keywords: Membrane protein; Photosynthesis; Photosystem II assembly; Thylakoid membrane