1.C.53 The Lactocyclicin Q (Lactocyclicin Q) Family

Lactococcus sp. strain QU 12, isolated from cheese, produces a cyclic bacteriocin termed lactocyclicin Q (Sawa et al., 2009). Lactocyclicin Q was purified from culture supernatant and has a unique antimicrobial spectrum, high level of protease resistance, and heat stability compared to other reported bacteriocins of lactic acid bacteria. This compound is composed of 61 aas that have a cyclic structure with linkage between the N and C termini by a peptide bond. It shows little similarity to any other antimicrobial peptides, including cyclic bacteriocins, but shows significant similarity to small proteins from Bacillus coagulans (EEN93214; 38% identity) and Paenibacillus larvae (ZP_02326427; 36% identity). It has a single TMS.

The reaction presumed to be catalyzed by Lactocyclicin Q is:

ions (in) ⇌ ions (out)

This family belongs to the Bacterial Bacteriocin (BB) Superfamily.



Sawa, N., T. Zendo, J. Kiyofuji, K. Fujita, K. Himeno, J. Nakayama, and K. Sonomoto. (2009). Identification and characterization of lactocyclicin Q, a novel cyclic bacteriocin produced by Lactococcus sp. strain QU 12. Appl. Environ. Microbiol. 75: 1552-1558.

van Belkum, M.J., L.A. Martin-Visscher, and J.C. Vederas. (2011). Structure and genetics of circular bacteriocins. Trends Microbiol. 19: 411-418.

Wescombe, P.A., M. Upton, P. Renault, R.E. Wirawan, D. Power, J.P. Burton, C.N. Chilcott, and J.R. Tagg. (2011). Salivaricin 9, a new lantibiotic produced by Streptococcus salivarius. Microbiology 157: 1290-1299.


TC#NameOrganismal TypeExample

Cyclic bacteriocin, Group I, Lactocyclicin Q (LycQ, 63 aas; 1 TMS) (Sawa et al., 2009van Belkum et al., 2011)


LcyQ of Lactococcus sp-strain QU12 (B9ZZY0)


The Lactocyclin homologue


Lactocyclicin homologue of Streptococcus mutans (C6STH0)


Uncharacterized protein of 85 aas and 2 TMSs

UP of Streptococcus macacae


Bacteriocin cerein 7B family protein of 91 aas and 2 TMSs

Bacteriocin of Streptococcus sobrinus


Putative toxic protein of 91 aas and 2 TMSs

Toxin of Pseudoxanthomonas sp.


Uncharacterized protein of 117 aas and 2 TMSs

UP of Xenorhabdus bovienii


Uncharacterized protein of 96 aas and 1 TMS. 

UP of Yokenella regensburgei


Uncharacterized protein of 72 aas and 2 TMSs.

UP of Xanthomonas albilineans