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Science 13 August 1993:
Vol. 261. no. 5123, pp. 891 - 894
DOI: 10.1126/science.261.5123.891
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Articles

Protein Catalysis of the Retinal Subpicosecond Photoisomerization in the Primary Process of Bacteriorhodopsin Photosynthesis

Li Song 1, M. A. El-Sayed 1, and J. K. Lanyi 2

1 Department of Chemistry and Biochemistry, University of California, Los Angeles Los Angeles, CA 90024-1569
2 Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92717

The rate of retinal photoisomerization in wild-type bacteriorhodopsin (wt bR) is compared with that in a number of mutants in which a positively charged (Arg82), a negatively charged (Asp85 or Asp212), or neutral hydrogen bonding (Asp115 or Tyr185) amino acid residue known to be functionally important within the retinal cavity is replaced by a neutral, non-hydrogen bonding one. Only the replacements of the charged residues reduced the photoisomerization rate of the 13-cis and all-trans isomers present in these mutants by factors of sim1/4 and sim1/20, respectively. Retinal photo- and thermal isomerization catalysis and selectivity in wt bR by charged residues is discussed in terms of the known protein structure, the valence-bond wave functions of the ground and excited state of the retinal, and the electrostatic stabilization interactions within the retinal cavity.

Submitted on April 27, 1993
Accepted on June 18, 1993


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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