Crystal structure of a protein repair methyltransferase from Pyrococcus furiosus with its L-isoaspartyl peptide substrate.Griffith, S.C., Sawaya, M.R., Boutz, D.R., Thapar, N., Katz, J.E., Clarke, S., Yeates, T.O.
(2001) J.Mol.Biol. 313: 1103-1116
- PubMed: 11700066
- DOI: 10.1006/jmbi.2001.5095
- Primary Citation of Related Structures:  1JG1, 1JG3, 1JG4
- PubMed Abstract:
Protein L-isoaspartyl (D-aspartyl) methyltransferases (EC 22.214.171.124) are found in almost all organisms. These enzymes catalyze the S-adenosylmethionine (AdoMet)-dependent methylation of isomerized and racemized aspartyl residues in age-damaged protein ...
Protein L-isoaspartyl (D-aspartyl) methyltransferases (EC 126.96.36.199) 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.
Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles 90095-1569, USA.