title: Identification and characterization of a methionine γ-lyase in the calicheamicin biosynthetic cluster of Micromonospora echinospora.
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.
authors.affiliation: Department of Chemistry and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong).
authors.forename: Haigang
authors.initials: H
authors.lastname: Song
authors.forename: Ri
authors.initials: R
authors.lastname: Xu
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Guo
mesh_terms: D000595:Amino Acid Sequence; D000617:Aminoglycosides / Q000096:biosynthesis; D064751:Ammonium Compounds / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002087:Butyrates / Q000737:chemistry / Q000378:metabolism; D019757:Carbon-Oxygen Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013437:Carbon-Sulfur Lyases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D003067:Coenzymes / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D053281:Enediynes; D015870:Gene Expression; D020035:Holoenzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008715:Methionine / Q000737:chemistry / Q000378:metabolism; D008847:Micromonospora / Q000201:enzymology* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family; D011732:Pyridoxal Phosphate / Q000737:chemistry* / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000378:metabolism
chemical_list: D000617:Aminoglycosides; D064751:Ammonium Compounds; D001426:Bacterial Proteins; D002087:Butyrates; D003067:Coenzymes; D053281:Enediynes; D020035:Holoenzymes; D013438:Sulfhydryl Compounds; C055955:calicheamicin gamma(1)I; C005231:methylmercaptan; D011732:Pyridoxal Phosphate; C005087:alpha-ketobutyric acid; D008715:Methionine; C022696:O-succinylhomoserine (thiol)-lyase; D019757:Carbon-Oxygen Lyases; D013437:Carbon-Sulfur Lyases; C021558:L-methionine gamma-lyase
keywords: biosynthesis; calicheamicins; enzyme catalysis; methionine gamma-lyase; protein structures