N-terminal sequences of subunits L and M of the photosynthetic reaction centre from Rhodospirillum rubrum G-9+. Separation of the subunits by gel filtration on hydroxypropylated Sephadex G 100 in organic solvents.
A new method has been developed by which subunits L and M of the photosynthetic reaction centre from Rhodospirillum rubrum G-9+ can be obtained in pure form, starting form freeze-dried chromatophore membranes. The method employs extraction into a mixture of chloroform/methanol and gel permeation chromatography on a column of hydroxypropylated Sephadex G 100. Cross-contamination of the purified subunits was less than 5% (mol/mol), as estimated by manual Edman degradation. Automated Edman degradation has been carried out with both subunits in a liquid-phase sequencer. 36 amino-acid residues of subunit L and 50 residues of subunit M could be unequivocally identified. In both cases, the sequence analyses came to a premature end as the signal sudden by dropped to the level of the accidental fluctuations of the phenylthiohydantoin-derivatives background. This effect is explained by the unusual susceptibility to peptide bond cleavage of certain threonine residues which probably underwent N leads to O acyl shift during the cleavage reactions. The N-terminal sequences have been compared to those of subunits L and M of the photosynthetic reactions centre from Rhodopseudomonas sphaeroides R-26 (sutton, M.R., Rosen, D., Feher, G. & Steiner, L.A. (1982) Biochemistry 21, 3842-3849). The homology among subunits L is close to 90% and thus markedly higher than that among subunits M (32%). This finding indicates a pre-eminent role of subunit L in the primary events of photosynthetic energy conversion.
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001426:Bacterial Proteins / Q000302:isolation & purification*; D002850:Chromatography, Gel / Q000379:methods; D003911:Dextrans; D046911:Macromolecular Substances; D008970:Molecular Weight; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins; D012247:Rhodospirillum rubrum / Q000378:metabolism*
D000596:Amino Acids; D001426:Bacterial Proteins; D003911:Dextrans; D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins; C040462:sephadex, 2-hydroxypropyl ether