Abstract
CalE6 is a previously uncharacterized protein involved in the biosynthesis of calicheamicins in Micromonospora echinospora. It is a pyridoxal-5'-phosphate-dependent enzyme and exhibits high sequence homology to cystathionine γ-lyases and cystathionine γ-synthases. However, it was found to be active towards methionine and to convert this amino acid into α-ketobutyrate, ammonium, and methanethiol. The crystal structure of the cofactor-bound holoenzyme was resolved at 2.0 Å; it contains two active site residues, Gly105 and Val322, specific for methionine γ-lyases. Modeling of methionine into the active site allows identification of the active site residues responsible for substrate recognition and catalysis. These findings support that CalE6 is a putative methionine γ-lyase producing methanethiol as a building block in biosynthesis of calicheamicins.
Keywords:
biosynthesis; calicheamicins; enzyme catalysis; methionine gamma-lyase; protein structures.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Aminoglycosides / biosynthesis
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Ammonium Compounds / chemistry
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Ammonium Compounds / metabolism
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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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Butyrates / chemistry
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Butyrates / metabolism
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Carbon-Oxygen Lyases / chemistry
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Carbon-Oxygen Lyases / genetics
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Carbon-Oxygen Lyases / metabolism
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Carbon-Sulfur Lyases / chemistry*
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Carbon-Sulfur Lyases / genetics
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Carbon-Sulfur Lyases / metabolism
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Catalytic Domain
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Coenzymes / chemistry*
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Coenzymes / metabolism
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Crystallography, X-Ray
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Enediynes
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Gene Expression
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Holoenzymes / chemistry*
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Holoenzymes / genetics
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Holoenzymes / metabolism
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Methionine / chemistry
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Methionine / metabolism
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Micromonospora / enzymology*
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Micromonospora / genetics
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Models, Molecular
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Molecular Sequence Data
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Multigene Family
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Pyridoxal Phosphate / chemistry*
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Pyridoxal Phosphate / metabolism
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Sequence Alignment
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Sequence Homology, Amino Acid
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Sulfhydryl Compounds / chemistry
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Sulfhydryl Compounds / metabolism
Substances
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Aminoglycosides
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Ammonium Compounds
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Bacterial Proteins
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Butyrates
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Coenzymes
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Enediynes
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Holoenzymes
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Sulfhydryl Compounds
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calicheamicin gamma(1)I
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methylmercaptan
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Pyridoxal Phosphate
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alpha-ketobutyric acid
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Methionine
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O-succinylhomoserine (thiol)-lyase
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Carbon-Oxygen Lyases
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Carbon-Sulfur Lyases
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L-methionine gamma-lyase