Dissecting the catalytic and substrate binding activity of a class II lanthipeptide synthetase BovM.

LanM proteins are the synthetases of the class II lanthipeptides, which are responsible for lanthionine or methyllanthionine formation in lanthipeptides. LanMs are bifunctional enzymes with N-terminal dehydratase and C-terminal cyclase domains. However, the catalytic and especially the substrate binding function of LanM are not fully investigated. In this study, we analyzed the function of conserved residues of BovM, which is the synthetase of lanthipeptide bovicin HJ50, with alanine substitution method. Mass spectrometry (MS) and surface plasmon resonance (SPR) analyses showed six hydrophilic residues (e.g. Asp247) were involved in the dehydration activity of BovM and four hydrophobic residues (e.g. Ile254) were responsible for the substrate binding of BovM. In addition, a conserved Asp155 was proposed to be general base in the elimination of phosphates during the dehydration reactions. This research of BovM shed a light on the catalytic and substrate binding mechanism of LanM proteins.