1dl5
From Proteopedia
PROTEIN-L-ISOASPARTATE O-METHYLTRANSFERASE
Structural highlights
FunctionPIMT_THEMA Catalyzes the methyl esterification of L-isoaspartyl residues in peptides and proteins that result from spontaneous decomposition of normal L-aspartyl and L-asparaginyl residues. It plays a role in the repair and/or degradation of damaged proteins. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBACKGROUND: Formation of isoaspartyl residues is one of several processes that damage proteins as they age. Protein L-isoaspartate (D-aspartate) O-methyltransferase (PIMT) is a conserved and nearly ubiquitous enzyme that catalyzes the repair of proteins damaged by isoaspartyl formation. RESULTS: We have determined the first structure of a PIMT from crystals of the T. maritima enzyme complexed to S-adenosyl-L-homocysteine (AdoHcy) and refined it to 1.8 A resolution. Although PIMT forms one structural unit, the protein can be divided functionally into three subdomains. The central subdomain closely resembles other S-adenosyl-L-methionine-dependent methyltransferases but bears a striking alteration of topological connectivity, which is not shared by any other member of this family. Rather than arranged as a mixed beta sheet with topology 6 upward arrow7 downward arrow5 upward arrow4 upward arrow1 upward arrow2 upward arrow3 upward arrow, the central sheet of PIMT is reorganized to 7 upward arrow6 downward arrow5 upward arrow4 upward arrow1 upward arrow2 upward arrow3 upward arrow. AdoHcy is largely buried between the N-terminal and central subdomains by a conserved and largely hydrophobic loop on one rim of the binding cleft, and a conserved Ser/Thr-rich beta strand on the other. The Ser/Thr-rich strand may provide hydrogen bonds for specific interactions with isoaspartyl substrates. The side chain of Ile-206, a conserved residue, crosses the cleft, restricting access to the donor methyl group to a deep well, the putative isoaspartyl methyl acceptor site. CONCLUSIONS: The structure of PIMT reveals a unique modification of the methyltransferase fold along with a site for specific recognition of isoaspartyl substrates. The sequence conservation among PIMTs suggests that the current structure should prove a reliable model for understanding the repair of isoaspartyl damage in all organisms. Crystal structure of protein isoaspartyl methyltransferase: a catalyst for protein repair.,Skinner MM, Puvathingal JM, Walter RL, Friedman AM Structure. 2000 Nov 15;8(11):1189-201. PMID:11080641[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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