Crystal structure of a protein repair methyltransferase from Pyrococcus furiosus with its l -isoaspartyl peptide substrate 1 1Edited by I. A. Wilson

Autor: Michael R. Sawaya, Nitika Thapar, Todd O. Yeates, Scott C. Griffith, Daniel R. Boutz, Steven Clarke, Jonathan E. Katz
Rok vydání: 2001
Předmět:
Zdroj: Journal of Molecular Biology. 313:1103-1116
ISSN: 0022-2836
DOI: 10.1006/jmbi.2001.5095
Popis: Protein l -isoaspartyl ( d -aspartyl) methyltransferases (EC 2.1.1.77) are found in almost all organisms. These enzymes catalyze the S-adenosylmethionine (AdoMet)-dependent methylation of isomerized and racemized aspartyl residues in age-damaged proteins as part of an essential protein repair process. Here, we report crystal structures of the repair methyltransferase at resolutions up to 1.2 A from the hyperthermophilic archaeon Pyrococcus furiosus. Refined structures include binary complexes with the active cofactor AdoMet, its reaction product S-adenosylhomocysteine (AdoHcy), and adenosine. The enzyme places the methyl-donating cofactor in a deep, electrostatically negative pocket that is shielded from solvent. Across the multiple crystal structures visualized, the presence or absence of the methyl group on the cofactor correlates with a significant conformational change in the enzyme in a loop bordering the active site, suggesting a role for motion in catalysis or cofactor exchange. We also report the structure of a ternary complex of the enzyme with adenosine and the methyl-accepting polypeptide substrate VYP( l -isoAsp)HA at 2.1 A. The substrate binds in a narrow active site cleft with three of its residues in an extended conformation, suggesting that damaged proteins may be locally denatured during the repair process in cells. Manual and computer-based docking studies on different isomers help explain how the enzyme uses steric effects to make the critical distinction between normal l -aspartyl and age-damaged l -isoaspartyl and d -aspartyl residues.
Databáze: OpenAIRE
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