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PucC and LhaA direct efficient assembly of the light‐harvesting complexes in Rhodobacter sphaeroides
Author(s) -
Mothersole David J.,
Jackson Philip J.,
Vasilev Cvetelin,
Tucker Jaimey D.,
Brindley Amanda A.,
Dickman Mark J.,
Hunter C. Neil
Publication year - 2016
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.13235
Subject(s) - rhodobacter sphaeroides , translocase , bacteriochlorophyll , biology , biophysics , protein subunit , light harvesting complex , photosynthetic reaction centre , membrane , membrane protein , photosystem ii , microbiology and biotechnology , biochemistry , photosynthesis , chromosomal translocation , gene
Summary The mature architecture of the photosynthetic membrane of the purple phototroph R hodobacter sphaeroides has been characterised to a level where an atomic‐level membrane model is available, but the roles of the putative assembly proteins LhaA and PucC in establishing this architecture are unknown. Here we investigate the assembly of light‐harvesting LH 2 and reaction centre‐light‐harvesting1‐ PufX ( RC ‐ LH 1‐ PufX ) photosystem complexes using spectroscopy, pull‐downs, native gel electrophoresis, quantitative mass spectrometry and fluorescence lifetime microscopy to characterise a series of lha A and puc C mutants. LhaA and PucC are important for specific assembly of LH 1 or LH 2 complexes, respectively, but they are not essential; the few LH 1 subunits found in Δ lha A mutants assemble to form normal RC ‐ LH 1‐ PufX core complexes showing that, once initiated, LH 1 assembly round the RC is cooperative and proceeds to completion. LhaA and PucC form oligomers at sites of initiation of membrane invagination; LhaA associates with RC s, bacteriochlorophyll synthase ( BchG ), the protein translocase subunit YajC and the YidC membrane protein insertase. These associations within membrane nanodomains likely maximise interactions between pigments newly arriving from BchG and nascent proteins within the SecYEG ‐ SecDF ‐ YajC ‐ YidC assembly machinery, thereby co‐ordinating pigment delivery, the co‐translational insertion of LH polypeptides and their folding and assembly to form photosynthetic complexes.