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Sub‐cellular location of F ts H proteases in the cyanobacterium S ynechocystis sp. PCC 6803 suggests localised PSII repair zones in the thylakoid membranes
Author(s) -
Sacharz Joanna,
Bryan Samantha J.,
Yu Jianfeng,
Burroughs Nigel J.,
Spence Edward M.,
Nixon Peter J.,
Mullineaux Conrad W.
Publication year - 2015
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12940
Subject(s) - thylakoid , biology , proteases , cytoplasm , cyanobacteria , protein subunit , chloroplast , microbiology and biotechnology , biochemistry , bacteria , enzyme , gene , genetics
Summary In cyanobacteria and chloroplasts, exposure to HL damages the photosynthetic apparatus, especially the D 1 subunit of P hotosystem II . To avoid chronic photoinhibition, a PSII repair cycle operates to replace damaged PSII subunits with newly synthesised versions. To determine the sub‐cellular location of this process, we examined the localisation of F ts H metalloproteases, some of which are directly involved in degrading damaged D 1. We generated transformants of the cyanobacterium S ynechocystis sp. PCC 6803 expressing GFP ‐tagged versions of its four F ts H proteases. The ftsH2–gfp strain was functional for PSII repair under our conditions. Confocal microscopy shows that F ts H 1 is mainly in the cytoplasmic membrane, while the remaining F ts H proteins are in patches either in the thylakoid or at the interface between the thylakoid and cytoplasmic membranes. HL exposure which increases the activity of the P hotosystem II repair cycle led to no detectable changes in F ts H distribution, with the F ts H 2 protease involved in D 1 degradation retaining its patchy distribution in the thylakoid membrane. We discuss the possibility that the F ts H 2– GFP patches represent P hotosystem II ‘repair zones’ within the thylakoid membranes, and the possible advantages of such functionally specialised membrane zones. Anti‐ GFP affinity pull‐downs provide the first indication of the composition of the putative repair zones.