Microsin J25 Precursor

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Microsin J25 precursor (McjA) is an antibiotic peptide that is potent against a range of Enterobacteriacae, including pathogenic strains of E. coli, Salmonella, and Shigella. It acts by inhibition of the bacterial DNA-dependent RNA polymerase (RNAP). In Salmonella newport, it can also act on the cytoplasmic membrane, producing alteration permeability and disruption of the subsequent gradient dissipation, which inhibits several processes essential for cell viability, such as oxygen consumption. It can also induce bacterial filamentation in susceptible cells in a non-SOS dependent way, but this phenotype may result from impaired transcription of genes coding for cell division proteins.

McjA is part of a group of genes that code for the antibiotic as well as confer immunity to it. McjB and McjC code for proteins that transform McjA - which has an N-terminal extension of 37 amino acids- into the mature 21 amino acid form, called MccJ25. McjD seems to be involved in conferring immunity.

The final form of the antibiotic, MccJ25, was at first believed to be cyclic, but actually turns out to have an unusual "lasso" structure. The backbone linkage (shown in yellow) between Gly1 and Gly8 forms a loop (in green) which the C-terminal tail (in purple) penetrates. Phe18 (in red) and Tyr20 (in blue) form a "lock" that keeps the C-terminal tail in place.

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Keywords: Antibiotic; Antimicrobial; Bacteriocin; Direct protein sequencing; Plasmid


  • View this protein's PDB entry at 1PP5
  • View this protein's SwissProt entry at MCJA_ECOLI
  • View this protein's NESG entry at ER142
  • To view this protein's coordinates click here


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