Abstract
Lantibiotics are a group of peptide‐based antimicrobial agents with unique structural characteristics which include unsaturated amino acids and thio‐ether rings. A bifunctional enzyme, lacticin 481 synthetase (LctM) is responsible for the maturation of a precursor peptide (LctA) to the lantibiotic lacticin 481. Experiments using MALDI‐TOF MS and Site‐directed mutagenesis revealed important residues of LctM which are responsible for dehydration of Ser and Thr residues in LctA. Briefly, Asp242 or Asp259 may be the base that accepts a proton from Ser/Thr of the substrate. Lys159 we suggest as a critical residue for phosphoryl transfer reaction and also aid phosphate elimination step as a general acid. Study also showed that two LctM mutants, Arg399Met and Thr405Ala, trapped phosphorylated Ser/Thr intermediates of LctA. We think that Arg399 or Thr405 work either as active site base which deprotonates the [alpha]‐carbon of a phosphate intermediate or activates another residue that is the actual base for deprotonation. We tested Arg399Met or Thr405Ala LctM for phosphorylation of Ser/Thr in peptides of various sequences and lengths. Based upon these results the Arg399Met and Thr405Ala mutants can be classified as general Ser/Thr kinase
Published Version
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