Photosystem II polypeptides

Gounaris K, Pick U, Barber J. Stoichiometry and mrnover of Photosystem II polypeptides. FEBS Lett 1987 211 94-98. 

Golden SS, Brusslan J, Haselkorn R. Expression of a family of psbA genes encoding a photosystem II polypeptide in the cyanobacterium Anacysds nidulans R2. EMBO J 1986 5 2789-2798. 

Darr, S.W.S, Machado, and C.J. Arntzen, 1981. Uniparental inheritance of a chloroplast photosystem II polypeptide controlling herbicide binding. Biochim. Biophys. Acta 634 219. 

All chloroplast-encoded polypeptides of photosystem n appear to be intrinsic membrane proteins with one or more hydrophobic membrane-spanning regions. The reaction centre complex is composed exclusively of chloroplast-encoded polypeptides, and both the associated antenna chlorophyll a-proteins are encoded in the chloroplast genome. In addition, a number of smaller polypeptides associated with photosystem n preparations have recently been shown to be chloroplast-encoded, but the role of these polypeptides is unknown. The chloroplast genes for photosystem II polypeptides are listed in Table 1 and their locations in the chloroplast genomes of wheat (Jriticum aestivum) and pea (Pisum sativum) are shown in Figure 1. 

Figure 2. Proposed models for the topology of photosystem II polypeptides in the thylakoid membrane. Membrtme-spaiming regions are drawn as cylindors.

The genes psbA-F were the first six chloroplast genes for polypeptides of photosystem II to be described. The remaining authenticated chloroplast genes for photosystem II polypeptides were all identified by V-reiminal amino acid sequ icing of snull polypeptides associated with photosystem II preparations. 

Photosystem II inhibitors, 13 288-294 plant growth regulator synthesis and function inhibitors, 13 304—307 Herbicide analysis methods, 13 312—313 Herbicide atomizer, 23 197 Herbicide binding, polypeptide... 

Although the structures of the plant reaction centers are not yet known in detail, photosystem II reaction centers resemble reaction centers of purple bacteria in several ways. The amino acid sequences of their two major polypeptides are homologous to those of the two polypeptides that hold the pigments in the bacterial reaction center. Also, the reaction centers of photosystem II contain a nonheme iron atom and two molecules of plastoquinone, a quinone that is closely related to ubiquinone (see fig. 15.10), and they contain one or more molecules of pheophytin a and several... 

The component that undergoes oxidation as photosystem II progresses from one S state to the next is a complex of four atoms of manganese bound to the two central polypeptides of the reaction center. P680t draws electrons from the Mn complex by way of a tyrosine in one of these polypeptides (see fig. 15.17). In the course of this reaction, the phenolic side chain of the tyrosine is oxidized transiently to a free radical. Although the structure of the Mn complex is not yet known, most of the transitions of the complex probably represent sequential oxidations of Mn atoms from the Mn(III) level to Mn(IV). 

Mattoo, A.K., U. Pick, H. Hoffmann-Falk, and M. Edelman (1981). The rapidly metabolized 32000-dalton polypeptide of the chloro-plast is the proteinaceous shield regulating photosystem II electron transport and mediating diuron herbicide sensitivity. Proc. Natl. Acad. Scl, 78 1572-1576. 

Nanba, O. and K. Satoh (1987). Isolation of a photosystem II reaction center consisting of D-l and D-2 polypeptides and cytochrome b-559. Proc. Natl. Acad. Sci., 84 109-112. 

Trebst, A. (1987). The three dimensional structure of the herbicide binding niche on the reaction center polypeptide of photosystem II. 

Trebst, A., B. Depka, B. Kraft, and U. Johanningmeier (1988). The QB-site modulates the conformation of the photosystem II reaction center polypeptides. Photosynthesis Res., 18 163-177. 

Iodolabeling studies on photosystem II particles from higher plants and cyanobacteria (221) and on a PSII complex (227) specifically labeled the herbicide-binding protein. As 1 is believed to donate electrons to Z, the secondary electron donor which is believed to accept electrons from the photosynthetic manganese complex, these experiments indicate a role for this protein on the oxidizing side of PSII. Consequently, Z must at least be located near, if not in, the herbicidebinding polypeptide (222). 

Photosynthesis in green plants is mediated by two kinds of membrane-bound, light-sensitive complexes—photosystem I (PS I) and photosystem II (PS II). Photosystem I typically includes 13 polypeptide chains, more than 60 chlorophyll molecules, a quinone (vitamin Kj), and three 4Fe-4S clusters. The total molecular mass is more than 800 kd. 

The transcriptions of several of the chloroplast genes are induced by light. The best studied example is the 32 kDa polypeptide of photosystem II [21]. It seems as if light induces the removal of a repressor or promotes the initiation of transcription... 

In green plants, algae, and cyanobacteria, the primary photochemical events of photosynthesis occur in the protein-pigment complex called photosystem II (PSII). PSII consists of more than ten polypeptide chains and a number of co-factors important for electron transport.(i, 6) The co-factors are believed bound to two homologous polypeptides approximately 32 kD in size (D1 and D2). Photoexcitation of the PSD reaction center drives single electron transfer from the primary electron donor, P, (probably a dimer of chlorophyll a) to the primary electron acceptor, one of two pheophytin a molecules. The reduced pheophytin transfers the electron on to a primary plastoquinone... 

Harrison MA and Melis A. (1992). Organization and stability of polypeptides associated with the chlorophyll a-b light-harvesting complex of photosystem-II. Plant Cell Physiol. 33, 627-637. 

Larrson UK, Sundby C and Andersson B. (1987). Characterization of two different subpopulations of spinach light-harvesting chlorophyll a-i-protein complex (LHC-II) polypeptide composition, phosphorylation pattern and association with photosystem-II. 

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