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Investigation into the source of electron transfer asymmetry in bacterial reaction centers.

Authors :
McDowell LM
Gaul D
Kirmaier C
Holten D
Schenck CC
Source :
Biochemistry [Biochemistry] 1991 Aug 27; Vol. 30 (34), pp. 8315-22.
Publication Year :
1991

Abstract

We have investigated the primary photochemistry of two symmetry-related mutants of Rhodobacter sphaeroides in which the histidine residues associated with the central Mg2+ ions of the two bacteriochlorophylls of the dimeric primary electron donor (His-L173 and His-M202) have been changed to leucine, affording bacteriochlorophyll (BChl)/bacteriopheophytin (BPh) heterodimers. Reaction centers (RCs) from the two mutants, (L)H173L and (M)H202L, have remarkably similar spectral and kinetic properties, although they are quite different from those of wild-type RCs. In both mutants, as in wild-type RCs, electron transfer to BPhL and not to BPhM is observed. These results suggest that asymmetry in the charge distribution of the excited BChl dimer (P*) in wild-type RCs (due to differing contributions of the two opposing intradimer charge-transfer states) contributes only modestly to the directionality of electron transfer. The results also suggest that differential orbital overlap of the two BChls of P with the chromophores on the L and M polypeptides does not contribute substantially to preferential electron transfer to BPhL.

Details

Language :
English
ISSN :
0006-2960
Volume :
30
Issue :
34
Database :
MEDLINE
Journal :
Biochemistry
Publication Type :
Academic Journal
Accession number :
1883819
Full Text :
https://doi.org/10.1021/bi00098a006