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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A gene from the cyanobacterium Synechocystis sp. PCC 6803 has been cloned and sequenced, and subsequently used to partially complement a bchP mutant of the purple photosynthetic bacterium Rhodobacter sphaeroides. This mutant is blocked in the terminal hydrogenation steps of bchla biosynthesis and possesses only bchl esterified with geranylgeraniol. It also has a reduced cellular level of the light-harvesting LH2 complex, and the 850 nm absorbance maximum of LH2 is red-shifted by approximately 6 nm. Upon heterologous expression of the Synechocystis bchP homologue, not only are hydrogenated forms of bchlaGG detectable, but the level of LH2 is increased and the red-shift reversed by several nm. We conclude that this gene, which we term chlP, encodes the enzyme catalysing the stepwise hydrogenation of geranylgeraniol to phytol during chla biosynthesis.
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PMID:Cloning, sequencing and functional assignment of the chlorophyll biosynthesis gene, chlP, of Synechocystis sp. PCC 6803. 876 14

The purple bacterium Rhodobacter sphaeroides provides a useful model system for studies of the assembly and dynamics of bacterial photosynthetic membranes. For the nascent developing membrane, proteomic analyses showed an ~2-fold enrichment in general membrane assembly factors, compared to chromatophores. When the protonophore carbonyl-cyanide m-chlorophenyl-hydrazone (CCCP) was added to an ICM inducing culture, an ~2-fold elevation in spectral counts vs. the control was seen for the SecA translocation ATPase, the preprotein translocase SecY, SecD and SecF insertion components, and chaperonins DnaJ and DnaK, which act early in the assembly process. It is suggested that these factors accumulated with their nascent polypeptides, as putative assembly intermediates in a functionally arrested state. Since in Synechocystis PCC 6803, a link has been established between Chl delivery involving the high-light HilD protein and the SecY/YidC-requiring cotranslational insertion of nascent polypeptides, such a connection between BChl biosynthesis and insertion and folding of nascent Rba. sphaeroides BChl binding proteins is likely to also occur. AFM imaging studies of the formation of the reaction center (RC)-light harvesting 1 (LH1) complex suggested a cooperative assembly mechanism in which, following the association between the RC template and the initial LH1 unit, addition of successive LH1 units to the RC drives the assembly process to completion. Alterations in membrane dynamics as the developing membrane becomes filled with LH2-rings were assessed by fluorescence induction/relaxation kinetics, which showed a slowing in RC electron transfer rate thought to mainly reflect alterations in donor side electron transfer. This was attributed to an increased distance for electron flow in cytochrome c2 between the RC and cytochrome bc1 complexes, as suggested in the current structural models. This article is part of a Special Issue entitled Organization and dynamics of bioenergetic systems in bacteria, edited by Prof Conrad Mullineaux.
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PMID:Development and dynamics of the photosynthetic apparatus in purple phototrophic bacteria. 2651 73