Slow solvation dynamics at the active site of an enzyme: implications for catalysis.
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.
Guha
Soumi
S
Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VIIM, Kolkata 700 054, India.
Sahu
Kalyanasis
K
Roy
Durba
D
Mondal
Sudip Kumar
SK
Roy
Siddhartha
S
Bhattacharyya
Kankan
K
D000604:Amino Acyl-tRNA Synthetases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis; D002942:Circular Dichroism; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000737:chemistry; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D017434:Protein Structure, Tertiary; D012343:RNA, Transfer / Q000378:metabolism; D012351:RNA, Transfer, Gln / Q000378:metabolism; D012997:Solvents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013379:Substrate Specificity; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
D012351:RNA, Transfer, Gln; D012997:Solvents; D005973:Glutamine; D014443:Tyrosine; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases; C020659:glutaminyl-tRNA synthetase; D003545:Cysteine; D006862:Hydrogen Sulfide