IN BACTERIAL REACTION CENTERS, A KEY RESIDUE SUPPRESSES MUTATIONAL BLOCKAGE OF 2 DIFFERENT PROTON-TRANSFER STEPS

Citation
J. Miksovska et al., IN BACTERIAL REACTION CENTERS, A KEY RESIDUE SUPPRESSES MUTATIONAL BLOCKAGE OF 2 DIFFERENT PROTON-TRANSFER STEPS, Biochemistry, 37(8), 1998, pp. 2077-2083
Citations number
35
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
Journal title
ISSN journal
0006-2960
Volume
37
Issue
8
Year of publication
1998
Pages
2077 - 2083
Database
ISI
SICI code
0006-2960(1998)37:8<2077:IBRCAK>2.0.ZU;2-5
Abstract
In reaction centers of Rhodobacter (Rb.) capsulatus, the M43Asn -->Asp substitution is capable of restoring rapid rates for delivery of the second proton to Q(B) in a mutant that lacks L212Glu, Flash-induced ab sorbance spectroscopy was used to show a nearly native rate for transf er of the second proton to Q(B) (congruent to 700 s(-1)) in the L212Gl n+M43Asp double-mutant reaction center; this rate was shown to decreas e more than 1000-fold in the photoincompetent L212Glu -->Gln mutant [M iksovska, J., Kalman, L., Maroti, P., Schiffer, M., Set,ban, P., and H anson, D. K, (1997) Biochemistry 36, 12216-12226]. In Rb, sphaeroides, the equivalent M44Asn -->Asp mutation was reported to restore the rat e of transfer of the first proton to a wild-type level when it is adde d to the L213Asp -->Asn photoincompetent mutant [Rongey, S. H., Paddoc k, M. L., Feher, G., and Okamura, M. Y. (1993) Proc, Natl. Acad. Sci. U.S.A. 90, 1325-1329]. It is remarkable that the same second-site muta tion can compensate for both of these mutations which severely impair reaction center function by blocking two different proton-transfer rea ctions. We suggest that residue M43Asp is situated in a key position w hich can link pathways for delivery of both the first and second proto ns; (involving structured water molecules) to Q(B).