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Role of tyrosine residue 264 of RecA for the binding of cofactor and DNA.

Authors
  • Eriksson, S
  • Nordén, B
  • Morimatsu, K
  • Horii, T
  • Takahashi, M
Type
Published Article
Journal
Journal of Biological Chemistry
Publisher
American Society for Biochemistry & Molecular Biology (ASBMB)
Publication Date
Jan 25, 1993
Volume
268
Issue
3
Pages
1811–1816
Identifiers
PMID: 8420956
Source
Medline
License
Unknown

Abstract

The tyrosine fluorescence of the RecA protein is quenched by about 15% upon binding of the cofactor analog adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S). This quenching is not observed with a modified RecA in which the tyrosine residue at position 264 (Tyr-264) is replaced for alanine by site-directed mutagenesis, a modification which also results in a decrease of binding affinity of cofactor. This indicates that Tyr-264 is responsible for the fluorescence change and that the residue is close to or within the cofactor binding site. Upon DNA binding, a change of tyrosine fluorescence is observed both with the modified protein and with wild type RecA, indicating that DNA binding affects the environment of other tyrosine residues than Tyr-264. However, the change is significantly smaller in the modified protein, suggesting that both Tyr-264 as well as other residue(s) may be affected by the DNA binding. Changed fluorescence properties of the remaining tyrosine residues as a result of a slightly different DNA binding mode of the modified protein are also possible. Tyr-264 may be an important residue for the allosteric effect induced by the cofactor for the binding of DNA to RecA. In the recent crystal structure of RecA-ADP published by Story and Steitz (Story, R.M., and Steitz, T. A. (1992) Nature 355, 374-376), ADP is stacked with Tyr-103 and does not interact with Tyr-264. The fact that we observe no interaction of ATP gamma S with Tyr-103 (as evidenced from absence of fluorescence change) but instead with Tyr-264 may suggest an important conformational difference between the RecA complexes with, respectively, ADP and ATP.

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