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 1 or 2 TMSs. The second subfamily (1.C.53.2) consists of bacterial proteins, all of which probably have 2 TMSs, fairly centrally located, but variable is size. They derive from a variety of bacteria and are distantly related to the proteins in subfamily 1. The annotations for these proteins vary considerable from DUF1269, general stress protein, ChaB family protein, and permease. The reaction presumed to be catalyzed by Lactocyclicin Q is: ions (in) ⇌ ions (out)
This family belongs to the Bacterial Bacteriocin (BB) Superfamily.
References:
Fannin, S., J. Rangel, A.P. Bodurin, T. Yu, B. Mistretta, S. Mali, P. Gunaratne, S.J. Bark, J.O. Ebalunode, A. Khan, W.R. Widger, and M. Sen. (2021). Functional and structural characterization of Hyp730, a highly conserved and dormancy-specific hypothetical membrane protein. Microbiologyopen 10: e1154.
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.
Examples:
TC#	Name	Organismal Type	Example
1.C.53.1.1	*Cyclic bacteriocin, Group I, Lactocyclicin Q (LycQ, 63 aas; 1 or 2 TMSs) (Sawa et al., 2009; van Belkum et al., 2011)*	Firmicutes	LcyQ of Lactococcus sp-strain QU12 (B9ZZY0)

1.C.53.1.2	The Lactocyclin homologue of 83 aas and 2 TMSs.	Firmicutes	*Lactocyclicin homologue of Streptococcus mutans* (C6STH0)**

1.C.53.1.3	Uncharacterized protein of 85 aas and 2 TMSs		UP of Streptococcus macacae

1.C.53.1.4	Bacteriocin cerein 7B family protein of 91 aas and 2 TMSs		Bacteriocin of Streptococcus sobrinus

1.C.53.1.5	Putative toxic protein of 91 aas and 2 TMSs		*Toxin of Pseudoxanthomonas* sp.**

1.C.53.1.6	Uncharacterized protein of 117 aas and 2 TMSs		UP of Xenorhabdus bovienii

1.C.53.1.7	Uncharacterized protein of 96 aas and 1 TMS.		UP of Yokenella regensburgei

1.C.53.1.8	Uncharacterized protein of 72 aas and 2 TMSs.		UP of Xanthomonas albilineans

Examples:
TC#	Name	Organismal Type	Example
1.C.53.2.1	DUF1269 domain containing protein of 152 aas and 2 TMSs.		DUF1269 protein of Flavobacterium limnosediminis

1.C.53.2.10	Membrane protein, Rv1234, of 175 aas and 2 TMSs. It is a non-essential protein that is induced during dormancy. A homologue in Micrococcus luteus, called Hyp730 (TC# 1.C.53.2.11), has been studied. Structural homology comparisons showed that Hyp730 is highly conserved and non-redundant in G+C rich Actinobacteria and other bacteria, and might be involved, under stress conditions, in an energy-saving process involving respiration during dormancy (Fannin et al. 2021).		Rv1234 of Mycobacterium tuberculosis

1.C.53.2.11	Functionally uncharacterized protein of 175 aas and 2 TMSs, Hyp730. It is a non-essential protein that is induced during dormancy. Structural homology comparisons showed that Hyp730 is highly conserved and non-redundant in G+C rich Actinobacteria and might be involved, under stress conditions, in an energy-saving process in respiration during dormancy (Fannin et al. 2021).		Hyp730 of Micrococcus luteus

1.C.53.2.2	General stress protein of 179 aas and 2 TMSs.		*GSP of Plectolyngbya* sp. WJT66-NPBG17 (algae metagenome)**

1.C.53.2.3	ChaB family protein of 257 aas and 2 TM		ChaB of Cylindrospermum stagnale

1.C.53.2.4	Magnesium transporter of 154 aas and 2 TMSs.		Mg²⁺ transporter of Brevibacterium rongguiense

1.C.53.2.5	DUF1269 domain-containing protein of 175 aas and 2 TMSs.		*DUF1269 domain protein of Granulicella* sp. 5B5**

1.C.53.2.6	Uncharacterized protein of 163 aas and 2 TMSs.		UP of Gloeothece citriformis

1.C.53.2.7	Uncharacterized protein of 160 aas and 2 TMSs.		UP of Nonomuraea phyllanthi

1.C.53.2.8	Signal transduction histidine kinase LytS of 227 aas and 2 TM		Putative his kinase of Gloeocapsopsis dulcis

1.C.53.2.9	Uncharacterized protein of 257 aas and 2 TMSs		UP of Varibaculum massiliense