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1: Biochemistry. 2005 Jun 28;44(25):8940-7.
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Slow solvation dynamics at the active site of an enzyme: implications for catalysis.

Guha S, Sahu K, Roy D, Mondal SK, Roy S, Bhattacharyya K.

Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VIIM, Kolkata 700 054, India.

Solvation dynamics at the active site of an enzyme, glutaminyl-tRNA synthetase (GlnRS), was studied using a fluorescence probe, acrylodan, site-specifically attached at cysteine residue C229, near the active site. The picosecond time-dependent fluorescence Stokes shift indicates slow solvation dynamics at the active site of the enzyme, in the absence of any substrate. The solvation dynamics becomes still slower when the substrate (glutamine or tRNA(Gln)) binds to the enzyme. A mutant Y211H-GlnRS was constructed in which the glutamine binding site is disrupted. The mutant Y211H-GlnRS labeled at C229 with acrylodan exhibited significantly different solvent relaxation, thus demonstrating that the slow dynamics is indeed associated with the active site. Implications for catalysis and specificity have been discussed.

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PMID: 15966719 [PubMed - indexed for MEDLINE]