title: NdhM Subunit Is Required for the Stability and the Function of NAD(P)H Dehydrogenase Complexes Involved in CO2 Uptake in Synechocystis sp. Strain PCC 6803.
abstract: The cyanobacterial type I NAD(P)H dehydrogenase (NDH-1) complexes play a crucial role in a variety of bioenergetic reactions such as respiration, CO2 uptake, and cyclic electron transport around photosystem I. Two types of NDH-1 complexes, NDH-1MS and NDH-1MS', are involved in the CO2 uptake system. However, the composition and function of the complexes still remain largely unknown. Here, we found that deletion of ndhM caused inactivation of NDH-1-dependent cyclic electron transport around photosystem I and abolishment of CO2 uptake, resulting in a lethal phenotype under air CO2 condition. The mutation of NdhM abolished the accumulation of the hydrophilic subunits of the NDH-1, such as NdhH, NdhI, NdhJ, and NdhK, in the thylakoid membrane, resulting in disassembly of NDH-1MS and NDH-1MS' as well as NDH-1L. In contrast, the accumulation of the hydrophobic subunits was not affected in the absence of NdhM. In the cytoplasm, the NDH-1 subcomplex assembly intermediates including NdhH and NdhK were seriously affected in the ΔndhM mutant but not in the NdhI-deleted mutant ΔndhI. In vitro protein interaction analysis demonstrated that NdhM interacts with NdhK, NdhH, NdhI, and NdhJ but not with other hydrophilic subunits of the NDH-1 complex. These results suggest that NdhM localizes in the hydrophilic subcomplex of NDH-1 complexes as a core subunit and is essential for the function of NDH-1MS and NDH-1MS' involved in CO2 uptake in Synechocystis sp. strain PCC 6803.
authors.affiliation: From the National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, 300 Fenglin Road, Shanghai 200032, China and.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: He
authors.affiliation: From the National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, 300 Fenglin Road, Shanghai 200032, China and.
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.affiliation: From the National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, 300 Fenglin Road, Shanghai 200032, China and.
authors.forename: Yaozong
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Renewable Energy Research Center, China University of Petroleum Beijing, 18 Fuxue Road, Changping, Beijing 102249, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Lv
authors.affiliation: Renewable Energy Research Center, China University of Petroleum Beijing, 18 Fuxue Road, Changping, Beijing 102249, China.
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Fu
authors.affiliation: From the National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, 300 Fenglin Road, Shanghai 200032, China and. Electronic address: mihl@sippe.ac.cn.
authors.forename: Hualing
authors.initials: H
authors.lastname: Mi
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport; D045331:Photosystem I Protein Complex / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism; D011808:Quinone Reductases / Q000378:metabolism*; D046939:Synechocystis / Q000201:enzymology* / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism
chemical_list: D045331:Photosystem I Protein Complex; D021122:Protein Subunits; D002734:Chlorophyll; D002245:Carbon Dioxide; C041831:NADH dehydrogenase (quinone); D011808:Quinone Reductases
keywords: carbon fixation; cyanobacteria; electron transfer complex; photosynthesis; respiration