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Identification Of Nsf Protein Requried For Stability Of NDH-1Complexes In Synechocystis Sp.PCC6803

Posted on:2015-10-15Degree:MasterType:Thesis
Country:ChinaCandidate:G F TongFull Text:PDF
GTID:2180330431968770Subject:Aquatic biology
Abstract/Summary:PDF Full Text Request
Cyanobacterial NADPH dehydrogenase (NDH-1) complexes are localized in the thylakoid membrane and participate in a variety of bioenergetic reactions, such as respiration, cyclic electron transport around photosystem I and CO2acquisition. The complex is widely present in bacteria, mammalian mitochondria and chloroplasts of higher plants. Over the past few years, significant achievements have been made in resolving the subunit compositions and functions of the multiple NDH-1complexes, however the maturation and assembly of NDH-1complexes still rarely reported. Recently, a homologue of CRR6protein, Slr1097, was found to be a maturation factor for NdhI subunit in Synechocystis sp. PCC6803. Despite the fact, the auxiliary proteins for NDH-1complexes are still poorly understood.In present study, to reveal the novel auxiliary proteins for NDH-1complexes, we applied the high-light screening strategy to isolate the mutants from Synechocystis6803transformed with a transposon-bearing library. Two mutants sensitive to high light for growth and impaired in NDH-CET were isolated. Both mutants had a tag in nsf gene. To confirm whether mutation of nsf results in the high light-sensitive phenotype, we constructed the nsf deletion mutant. Deletion of Nsf protein caused a significant reduction of Ndh subunits and impeded efficient assembly of NDH-1complexes on the thylakoid membrane. Further, Nsf protein located in the membrane fraction, but is not a novel subunit of NDH-1complexes, indicating that the Nsf protein may be a novel auxiliary protein for stabilization of NDH-1complexes. This possibility was reinforced by the facts that the increasing of Ndh subunits and assembly intermediate about140kDa from the cytoplasm fraction in△nsf mutant. It is likely that deletion of Nsf protein made NDH-1complexes unstable in thylakoid membrane, thus falling into the cytoplasm.In conclusion, this study first identified the Nsf protein, a novel membrane protein for stabilization of NDH-1complexes in Synechocystis6803. Deletion of Nsf protein caused a significant reduction of Ndh subunits and impeded efficient assembly of NDH-1complexes, thereby impairing the NDH-CET activity and resulting in a high light sensitive growth phenotype.
Keywords/Search Tags:cyanobacteria NDH-1complex, NDH-CET, Nsf, Assembly
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