Antimicrobial Peptide AP00480






Microcin J25 (MccJ25, formerly microcin 25, Mcc25; Gly-rich; lactam; a class 2 lasso peptide; class 1 microcins, bacteriocins, Gram-negative bacteria, prokaryotes; XXJ; UCSB1a; BBpol; revisited)



Escherichia coli AY25








Net charge:



Hydrophobic residue%:



Boman Index:

-0.64 kcal/mol


3D Structure:






SwissProt ID:

PDB ID: 1Q71   Go to PDB





Crucial residues:

Cyclic structure. Y9 is important for the second mechanism (2009 FEMS Microbio Lett 300: 90-96).


Additional info:

Secreted by E. coli AY25 to inhibit the growth of other Gram-negative bacteria. Active against E. coli BM21 (MIC 0.08-5 ug/ml), E. coli AB1133 (MIC 0.02-2.5 ug/ml), E. coli RYC816 (MIC 0.04-2.5 ug/ml), E. coli AY29 (0.04 in LB), and S. newport (MIC 0.01 ug/ml). MccJ25 (formerly Mcc25) is the single representative of the immunity group J. Four plasmid genes (plasmid-encoded) are required for MccJ25 biosyntheis: mcjA encodes the precursor protein, mcjB and mcjC encode two processing enzymes to generate mature peptide, and mcjD encodes the immunity protein (McjD), a member of the ABC transporter family. Immunity is achieved by active efflux of the processed peptide. Bacterial mutants resistant to MccJ25 can taken in the peptide via the outer membrane protein FhuA (the iron siderophore receptor) and inner membrane proteins TonB, ExbD, ExbB and SbmA. (MOA): It works by dual mechanism, interaction with RNA polymerase or membrane respiratory enzyme chain(Bellomio et al., 2007).

Old Structure: Originally proposed as a head-to-tail cyclic peptide (Blond 1999). Current structure (2003): MccJ25 has an unusual lariat-protoknot ("threaded lasso") structure consisting of an eight aa residue ring formed between the backbone NH of residue Gly1 and the side chain CO of residue Glu8 (XXCsb) (Wilson et al, 2003; Rosenqren et al., 2003). You can rotate, zoom, and view the 3D structure here in the PDB. The 13-residue tail loops back and pass through the ring and locked via aromatic rings of residues F19 and Y20 (see the structure in PDB). Systematic structure-activity analysis of MccJ25 revealed that only three in the ring and one in the tail are important for this peptide production. Furthermore, two residues in the ring and four in the threaded segment of the tail are essential for transcription inhibition (JBC 2008; 37: 25589-25595). It showed prolong effect in an animal model:mouse infection model (Lopez et al., 2007). The crystal structure of this peptide in complex with the bacterial RNA polymerase (RNAP) has also been determined (Braffman et al., 2019). MccJ25 binds deep within the secondary channel in a manner expected to interfere with NTP substrate binding.

This lasso fold is used as a stable peptide scaffold for grafting therapeutic peptides to enhance peptide stability (Hegemann et al., 2014). You can rotate, zoom, and view the 3D structure here in the PDB. Updated 2/2010; 10/2012; 2/2014; Jan2016; 7/2016; 9/2017; Jan2019.



Microcin 25, a novel antimicrobial peptide produced by Escherichia coli.



Salomón RA, Farías RN.1992



J Bacteriol. 1992 Nov;174(22):7428-35. PubMed.


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