Abstract
The methyl substituents in products of trans-acyltransferase assembly lines are usually incorporated by S-adenosyl-methionine (SAM)-dependent methyltransferase (MT) domains. The gem-dimethyl moieties within the polyketide disorazol are installed through the iterative action of an MT in the third module of its assembly line. The 1.75-Å-resolution crystal structure of this MT helps elucidate how it catalyzes the addition of two methyl groups. Activity assays of point mutants on β-ketoacyl chains linked to an acyl carrier protein and N-acetylcysteamine provide additional insights into the roles of active site residues. The replacement of an alanine with a phenylalanine at an apparent gatekeeping position resulted in more monomethylation than dimethylation. MTs may form an interface with ketoreductases (KRs) and even mediate the docking of trans-acyltransferase assembly line polypeptides through this association.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Alcohol Oxidoreductases / chemistry
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Alcohol Oxidoreductases / metabolism
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Amino Acid Sequence
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Bacterial Proteins / chemistry
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Catalytic Domain / genetics
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Crystallography, X-Ray
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Methylation
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Methyltransferases / chemistry*
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Methyltransferases / genetics
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Methyltransferases / metabolism
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Models, Molecular
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Molecular Structure
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Mutation
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Myxococcales / enzymology
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Oxazoles / chemistry
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Oxazoles / metabolism
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Polyketide Synthases / chemistry*
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Polyketide Synthases / genetics
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Polyketide Synthases / metabolism
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Polyketides / chemistry
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Polyketides / metabolism
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Protein Binding
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Protein Domains
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Sequence Alignment
Substances
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Bacterial Proteins
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Oxazoles
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Polyketides
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Polyketide Synthases
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Alcohol Oxidoreductases
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Methyltransferases