UNEXPECTED SIMILARITIES OF THE B800-850 LIGHT-HARVESTING COMPLEX FROM RHODOSPIRILLUM-MOLISCHIANUM TO THE B870 LIGHT-HARVESTING COMPLEXES FROM OTHER PURPLE PHOTOSYNTHETIC BACTERIA

被引:81
作者
GERMEROTH, L
LOTTSPEICH, F
ROBERT, B
MICHEL, H
机构
[1] MAX PLANCK INST BIOPHYS,MOLEK MEMBRANBIOL ABT,W-6000 FRANKFURT,GERMANY
[2] CE SACLAY,DBCM,CNRS,URA 1290,BIOPHYS PROT & MEMBRANES SECT,F-91191 GIF SUR YVETTE,FRANCE
[3] UNIV MUNICH,MAX PLANCK INST BIOCHEM,GENZENTRUM,W-8033 MARTINSRIED,GERMANY
关键词
D O I
10.1021/bi00072a017
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The B800-850 light-harvesting complex (also called LH2) was isolated from photosynthetic membranes of Rhodospirillum molischianum DSM 119 using molecular sieve and ion-exchange chromatography. Its two bacteriochlorophyll a-binding polypeptides (alpha-subunit and beta-subunit) were purified with a reverse-phase HPLC system. The complete amino acid sequences of both subunits have been determined. The alpha- and beta-subunits consist of 56 and 45 amino acids, respectively, corresponding to molecular weights of 5939 and 5133. In contrast to the B800-850 complexes from other photosynthetic bacteria, the native B800-850 complex from Rs. molischianum is most likely an octamer of monomers with a stoichiometry of three bacteriochlorophyll a and 1.5 lycopenes per alpha,beta-subunit. Resonance Raman spectra provide evidence for a 5-coordinated Mg2+ in the BChl, and a carotenoid mainly in the all-trans configuration. A comparison between resonance Raman data from different photosynthetic bacteria indicates that the BChl a-binding site of the B800-850 complex from Rs. molischianum is more similar to the B870 complexes (also called LH1) than to the B800-850 complexes of other photosynthetic bacteria. Sequence similarities especially between the beta-subunits of the B800-850 complex of Rs. molischianum and the B870 and B800-850 complexes of other photosynthetic bacteria agree with this result and provide information on the mode of pigment binding in bacterial antenna complexes.
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页码:5615 / 5621
页数:7
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