FIG 2.

The mcc-like operon of H. minutum DSM 14724 and its products. (A) Organization of the mcc-like gene cluster from H. minutum DSM 14724. Genes are represented by colored arrows, with functional predictions corresponding to each color shown in the key beneath. (B) The mechanism of MccB-mediated adenylation of an MccA precursor peptide (3). (C) MALDI-TOF MS spectra of products of in vitro reactions between chemically synthesized H. minutum MccA₁ and MccA₂ precursor peptides and recombinant MccB₁^Hmi and MccB₂^Hmi enzymes in the presence of ATP. Spectra shown at the top are controls (no MccB enzyme added). The mass difference of 329 Da between MccA₁ (m/z 3,926.2) and MccA₂ (m/z 4,767.6) mass ions and the mass ions of the reaction products (m/z 4,255.2 and m/z 5,096.6, correspondingly) matches the modification with AMP; the MH⁺ ion at m/z 4,749.6 present in reaction mixtures containing MccA₂^Hmi and MccB₂^Hmi is a succinimide intermediate of the nucleotidyl transfer reaction.