title: Functional Characterization of the Subunits N, H, J, and O of the NAD(P)H Dehydrogenase Complexes in Synechocystis sp. Strain PCC 6803.
abstract: The cyanobacterial NAD(P)H dehydrogenase (NDH-1) complexes play crucial roles in variety of bioenergetic reactions such as respiration, CO2 uptake, and cyclic electron transport around PSI. Recently, substantial progress has been made in identifying the composition of subunits of NDH-1 complexes. However, the localization and the physiological roles of several subunits in cyanobacteria are not fully understood. Here, by constructing fully segregated ndhN, ndhO, ndhH, and ndhJ null mutants in Synechocystis sp. strain PCC 6803, we found that deletion of ndhN, ndhH, or ndhJ but not ndhO severely impaired the accumulation of the hydrophilic subunits of the NDH-1 in the thylakoid membrane, resulting in disassembly of NDH-1MS, NDH-1MS', as well as NDH-1L, finally causing the severe growth suppression phenotype. In contrast, deletion of NdhO affected the growth at pH 6.5 in air. In the cytoplasm, either NdhH or NdhJ deleted mutant, but neither NdhN nor NdhO deleted mutant, failed to accumulate the NDH-1 assembly intermediate consisting of NdhH, NdhJ, NdhK, and NdhM. Based on these results, we suggest that NdhN, NdhH, and NdhJ are essential for the stability and the activities of NDH-1 complexes, while NdhO for NDH-1 functions under the condition of inorganic carbon limitation in Synechocystis sp. strain PCC 6803. We discuss the roles of these subunits and propose a new NDH-1 model.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, Shanghai 200032, China.
authors.forename: Zhihui
authors.identifier: 0000-0003-4184-8377
authors.initials: Z
authors.lastname: He
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, Shanghai 200032, China mihl@sippe.ac.cn.
authors.forename: Hualing
authors.identifier: 0000-0003-1021-8372
authors.initials: H
authors.lastname: Mi
mesh_terms: D000388:Air; D003593:Cytoplasm / Q000378:metabolism; D017353:Gene Deletion; D052836:Heterotrophic Processes; D008027:Light; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000378:metabolism*; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D010641:Phenotype; D011485:Protein Binding; D021122:Protein Subunits / Q000378:metabolism*; D015203:Reproducibility of Results; D046939:Synechocystis / Q000201:enzymology* / Q000254:growth & development
chemical_list: D009097:Multienzyme Complexes; D021122:Protein Subunits; D009252:NADPH Dehydrogenase