title: Characterization of NocL involved in thiopeptide nocathiacin I biosynthesis: a [4Fe-4S] cluster and the catalysis of a radical S-adenosylmethionine enzyme.
abstract: The radical S-adenosylmethionine (AdoMet) enzyme superfamily is remarkable at catalyzing chemically diverse and complex reactions. We have previously shown that NosL, which is involved in forming the indole side ring of the thiopeptide nosiheptide, is a radical AdoMet enzyme that processes L-Trp to afford 3-methyl-2-indolic acid (MIA) via an unusual fragmentation-recombination mechanism. We now report the expansion of the MIA synthase family by characterization of NocL, which is involved in nocathiacin I biosynthesis. EPR and UV-visible absorbance spectroscopic analyses demonstrated the interaction between L-Trp and the [4Fe-4S] cluster of NocL, leading to the assumption of nonspecific interaction of [4Fe-4S] cluster with other nucleophiles via the unique Fe site. This notion is supported by the finding of the heterogeneity in the [4Fe-4S] cluster of NocL in the absence of AdoMet, which was revealed by the EPR study at very low temperature. Furthermore, a free radical was observed by EPR during the catalysis, which is in good agreement with the hypothesis of a glycyl radical intermediate. Combined with the mutational analysis, these studies provide new insights into the function of the [4Fe-4S] cluster of radical AdoMet enzymes as well as the mechanism of the radical-mediated complex carbon chain rearrangement catalyzed by MIA synthase.
authors: State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China.
authors: Qi
authors: Q
authors: Zhang
authors: Dandan
authors: D
authors: Chen
authors: Jun
authors: J
authors: Lin
authors: Rijing
authors: R
authors: Liao
authors: Wei
authors: W
authors: Tong
authors: Zhinan
authors: Z
authors: Xu
authors: Wen
authors: W
authors: Liu
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D004252:DNA Mutational Analysis; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000378:metabolism; D005609:Free Radicals; D036341:Intercellular Signaling Peptides and Proteins; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010455:Peptides / Q000737:chemistry*; D012436:S-Adenosylmethionine / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan / Q000737:chemistry
chemical_list: D005609:Free Radicals; D036341:Intercellular Signaling Peptides and Proteins; D007506:Iron-Sulfur Proteins; D010455:Peptides; C463319:nocathiacin I; D012436:S-Adenosylmethionine; D014364:Tryptophan