Molecular genetic studies on the light harvesting - reaction centre (LH-RC) genes in the purple non-sulphur bacterium Blastochloris viridis

QR Microbiology;QH426 Genetics

Reksodipuro, Adhie Dwi Putranto ; Cogdell, Richard

University:University of Glasgow

Department:Institute of Molecular Cell and Systems Biology

关键词: Blastochloris viridis, Light Harvesting, Reaction Centre, Protein Structure, Genes, Sequence;   

Others  :  http://theses.gla.ac.uk/618/1/2009reksodipuromsc%28r%29.pdf

来源: University of Glasgow

【 摘 要 】

The 3D structure of Blastochloris (Bl.) viridis photosynthetic reaction centre (RC) was the first membrane protein structure determined by X-ray crystallization (Deisenhofer, et al., 1984; Deisenhofer, et al., 1985). At the same time, Michel et al determined the amino acid sequence of the reaction centre polypeptides (Michel, 1982; Michel, et al., 1985; Michel, et al., 1986; Wiessner, et al., 1990). However, recent investigations on a high resolution protein structure of this RC (Roszak, et al., unpublished observations) have found that several amino acids positions in the sequence did not fit the newer, higher resolution structure. The aim of this project, therefore, was to re-sequence the genes of the β and α subunits of the light-harvesting complex (LHC) and the L, M, H and Cytochrome c subunits of photosynthetic reaction centre (RC) from Blastochloris (Bl.) viridis to see if new sequence data would produce a better fit to the high resolution x-ray structure. All these genes were re-sequenced and the following changes were found; 5 changes for pufM (M29, M63, M70, M74 and M164), 8 for pufC (C43, C77, C84, C252, C277, C287, C288 and C323), and 2 for puhA (H216 and H256). The new amino acids that replaced the previous sequence at each position in PufM were as follows; Ile for Val (M29), Ala for Ser (M63), Gly for Leu (M70), Leu for Ala (M74) and Ala for Thr (M164), for PufC: Pro for Ala (C43), Met for Ile (C77), Glu for Gln (C84), Ser for Thr (C252), Met for Leu (C277), Thr for Ala (C287), Val for Ser (C288) and Gln for Lys (C323),and finally, for PuhA: Asp for Glu (H216) and Ala for Ser (H256). The new sequences were then fitted into the electron density maps of the higher resolution crystal structure. The changes in the primary structure of the polypeptides resulted in a much better fit. In particular the new sequence data resulted in a significant change in the structure of the reaction centre carotenoid so that it is now much more consistent with data from other reaction centre structures.