Microcin

Microcins are very small bacteriocins, composed of relatively few amino acids. For this reason, they are distinct from their larger protein cousins. The classic example is microcin V, of Escherichia coli. Subtilosin A is another bacteriocin from Bacillus subtilis. The peptide has a cyclized backbone and forms three cross-links between the sulphurs of Cys13, Cys7 and Cys4 and the alpha-positions of Phe22,Thr28 and Phe31.[1]

Subtilosin_A
structure of Subtilosin A
Identifiers
Symbol	Subtilosin_A
Pfam	PF11420
InterPro	IPR021539
TCDB	1.C.84
OPM superfamily	379
OPM protein	1pxq
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

Microcins produced by commensal E. coli strains target and eliminate enteric pathogens such as Salmonella enterica by mimicking the siderophores the pathogens use for iron scavenging. Microcins also help commensal strains of E. coli outcompete pathogenic strains.[2]

BACTIBASE[3][4] database is an open-access database for bacteriocins including microcins.

References

1. Kawulka KE, Sprules T, Diaper CM, Whittal RM, McKay RT, Mercier P, Zuber P, Vederas JC (March 2004). "Structure of subtilosin A, a cyclic antimicrobial peptide from Bacillus subtilis with unusual sulfur to alpha-carbon cross-links: formation and reduction of alpha-thio-alpha-amino acid derivatives". Biochemistry. 43 (12): 3385–95. doi:10.1021/bi0359527. PMID 15035610.
2. Tine Hesman Saey, "Tiny toxic proteins help gut bacteria defeat rivals", Science News Magazine Vol. 190, No. 12, December 10, 2016, p. 5
3. Hammami R, Zouhir A, Ben Hamida J, Fliss I (2007). "BACTIBASE: a new web-accessible database for bacteriocin characterization". BMC Microbiology. 7: 89. doi:10.1186/1471-2180-7-89. PMC 2211298. PMID 17941971.
4. Hammami R, Zouhir A, Le Lay C, Ben Hamida J, Fliss I (2010). "BACTIBASE second release: a database and tool platform for bacteriocin characterization". BMC Microbiology. 10: 22. doi:10.1186/1471-2180-10-22. PMC 2824694. PMID 20105292.