1.C.126. The HlyC Haemolysin (HlyC) Family

The hemolysin C of Brachyspira hyodysenteriae (268 aas; ter Huurne et al., 1994Hyatt and Joens 1997) and the Co2+-resistance protein, CorC of Salmonella typhimurium (273 aas; with one putative TMS (residues 163-181)) are homologous throughout most of their lengths to each other. They are also homologous to the C-terminal portions of 5 close paralogues in Bacillus subtilis, all of which are about 440 aas long and have an N-terminal 4 TMS domain. One representative B. subtilis paralogue is YrkA (434 aas; P54428). The CorC protein was believed to function as an auxiliary protein to the CorA Co2+/Mg2+ channel of S. typhimurium (Gibson et al., 1991). CorA is a member of the Metal Ion Transporter (MIT) family of α-type channels (TC #1.A.35). The HlyC family corresponds to SwissProt family UPF0053. MstE (1.A.26.1.2), CLC (2.A.49.6.1) and HlyC/CorC may all share a hydrophilic domain, and members of the HlyC family lack the 4 TMS transmembrane region and therefore are probably not transporters (see below).

The bacterial proteins, YrkA and YhdP have three recognized domains: the 4-TMS DUF21 domain (residues 1-170), a nucleotide binding CBS domain (residues 225-335) and a CorC/HlyC domain (residues 360-430).  The mammalian homologues have at least the first two of these domains which are preceded by an N-terminal TMS and an unidentified hydrophilic domain. The bacterial HlyC and CorC proteins (1.C.126.1.1 and 1.C.126.1.2) lack the 4 TMS DUF21 domain, but have the CBS and CorC/HlyC domains. Only the proteins with the DUF21 domain are likely to be transporters.  The evidence is consistent with the conclusion that these homologues form divalent-cation-specific porters, possibly exporters.



This family belongs to the CNNM/HlyC Superfamily.



Brandao K., Deason-Towne F., Perraud AL. and Schmitz C. (2013). The role of Mg2+ in immune cells. Immunol Res. 55(1-3):261-9.

Gibson, M.M., Bagga, D.A., Miller, C.G., and Maguire, M.E. (1991). Magnesium transport in Salmonella typhimurium: the influence of new mutations conferring Co2+ resistance on the CorA Mg2+ transport system. Mol Microbiol. 5: 2753-2762.

Quamme GA. (2010). Molecular identification of ancient and modern mammalian magnesium transporters. Am J Physiol Cell Physiol. 298(3):C407-29.

Arjona, F.J. and J.H.F. de Baaij. (2018). CrossTalk opposing view: CNNM proteins are not Na /Mg exchangers but Mg transport regulators playing a central role in transepithelial Mg (re)absorption. J. Physiol. 596: 747-750.

Chen, Y.S., G. Kozlov, R. Fakih, Y. Funato, H. Miki, and K. Gehring. (2018). The cyclic nucleotide-binding homology domain of the integral membrane protein CNNM mediates dimerization and is required for Mg efflux activity. J. Biol. Chem. [Epub: Ahead of Print]

Corral-Rodriguez MA., Stuiver M., Abascal-Palacios G., Diercks T., Oyenarte I., Ereno-Orbea J., de Opakua AI., Blanco FJ., Encinar JA., Spiwok V., Terashima H., Accardi A., Muller D. and Martinez-Cruz LA. (2014). Nucleotide binding triggers a conformational change of the CBS module of the magnesium transporter CNNM2 from a twisted towards a flat structure. Biochem J. 464(1):23-34.

de Baaij, J.H., M. Stuiver, I.C. Meij, S. Lainez, K. Kopplin, H. Venselaar, D. Müller, R.J. Bindels, and J.G. Hoenderop. (2012). Membrane topology and intracellular processing of cyclin M2 (CNNM2). J. Biol. Chem. 287: 13644-13655.

Funato, Y., D. Yamazaki, and H. Miki. (2017). Renal function of cyclin M2 Mg2+ transporter maintains blood pressure. J Hypertens 35: 585-592.

Funato, Y., K. Furutani, Y. Kurachi, and H. Miki. (2018). CrossTalk proposal: CNNM proteins are Na /Mg exchangers playing a central role in transepithelial Mg (re)absorption. J. Physiol. 596: 743-746.

Funato, Y., K. Furutani, Y. Kurachi, and H. Miki. (2018). Rebuttal from Yosuke Funato, Kazuharu Furutani, Yoshihisa Kurachi and Hiroaki Miki. J. Physiol. 596: 751.

Giménez-Mascarell, P., I. Oyenarte, S. Hardy, T. Breiderhoff, M. Stuiver, E. Kostantin, T. Diercks, A.L. Pey, J. Ereño-Orbea, M.L. Martínez-Chantar, R. Khalaf-Nazzal, F. Claverie-Martin, D. Müller, M.L. Tremblay, and L.A. Martínez-Cruz. (2017). Structural Basis of the Oncogenic Interaction of Phosphatase PRL-1 with the Magnesium Transporter CNNM2. J. Biol. Chem. 292: 786-801.

Gómez-García, I., M. Stuiver, J. Ereño, I. Oyenarte, M.A. Corral-Rodríguez, D. Müller, and L.A. Martínez-Cruz. (2012). Purification, crystallization and preliminary crystallographic analysis of the CBS-domain pair of cyclin M2 (CNNM2). Acta Crystallogr Sect F Struct Biol Cryst Commun 68: 1198-1203.

Goytain, A., and G.A. Quamme. (2005). Functional characterization of ACDP2 (ancient conserved domain protein), a divalent metal transporter. Physiol Genomics. 22: 382-389.

Gulerez, I., Y. Funato, H. Wu, M. Yang, G. Kozlov, H. Miki, and K. Gehring. (2016). Phosphocysteine in the PRL-CNNM pathway mediates magnesium homeostasis. EMBO Rep 17: 1890-1900.

Hirata, Y., Y. Funato, and H. Miki. (2014). Basolateral sorting of the Mg²⁺ transporter CNNM4 requires interaction with AP-1A and AP-1B. Biochem. Biophys. Res. Commun. 455: 184-189.

Hirata, Y., Y. Funato, Y. Takano, and H. Miki. (2014). Mg2+-dependent interactions of ATP with the cystathionine-β-synthase (CBS) domains of a magnesium transporter. J. Biol. Chem. 289: 14731-14739.

Hyatt, D.R. and L.A. Joens. (1997). Analysis of the lytic activity of the Serpulina hyodysenteriae hemolysin. Infect. Immun. 65: 4877-4879.

Ishii, T., Y. Funato, O. Hashizume, D. Yamazaki, Y. Hirata, K. Nishiwaki, N. Kono, H. Arai, and H. Miki. (2016). Mg2+ Extrusion from Intestinal Epithelia by CNNM Proteins Is Essential for Gonadogenesis via AMPK-TORC1 Signaling in Caenorhabditis elegans. PLoS Genet 12: e1006276.

Islam, Z., N. Hayashi, H. Inoue, T. Umezawa, Y. Kimura, H. Doi, M.F. Romero, S. Hirose, and A. Kato. (2014). Identification and lateral membrane localization of cyclin M3, likely to be involved in renal Mg2+ handling in seawater fish. Am. J. Physiol. Regul Integr Comp Physiol 307: R525-537.

Sałamaszyńska-Guz, A. and D. Klimuszko. (2008). Functional analysis of the Campylobacter jejuni cj0183 and cj0588 genes. Curr. Microbiol. 56: 592-596.

Schäffers, O.J.M., J.G.J. Hoenderop, R.J.M. Bindels, and J.H.F. de Baaij. (2018). The rise and fall of novel renal magnesium transporters. Am. J. Physiol. Renal Physiol 314: F1027-F1033.

Simonin A. and Fuster D. (2010). Nedd4-1 and beta-arrestin-1 are key regulators of Na+/H+ exchanger 1 ubiquitylation, endocytosis, and function. J Biol Chem. 285(49):38293-303.

Sponder, G., S. Svidova, M. Schweigel, J. Vormann, and M. Kolisek. (2010). Splice-variant 1 of the ancient domain protein 2 (ACDP2) complements the magnesium-deficient growth phenotype of Salmonella enterica sv. typhimurium strain MM281. Magnes Res 23: 105-114.

ter Huurne, A.A., Muir, S., van Houten, M., van der Zeijst, B.A., Gaastra, W., and Kusters, J.G. (1994). Characterization of three putative Serpulina hyodysenteriae hemolysins. Microb Pathog. 16: 269-282.

Turner, M.S. and J.D. Helmann. (2000). Mutations in multidrug efflux homologs, sugar isomerases, and antimicrobial biosynthesis genes differentially elevate activity of the σX and σW factors in Bacillus subtilis. J. Bacteriol. 182: 5202-5210.


TC#NameOrganismal TypeExample

Hemolysin C, HlyC or TlyC, of 268 aas.  Pore formation was demonstrated by the inhibition of hemolysis with molecules of 2.0 to 2.3 nm in diameter and the release of 86rubidium from erythrocytes without hemoglobin release after exposure to native hemolysin (Hyatt and Joens 1997).


HlyC of Brachyspira (Treponema, Serpulina) hyodysenteriae (Q54318)


Co2+-resistance protein, CorC, of 292 aas and 0 TMSs (Sponder et al. 2010).  The E. coli orthologue (P6AE78) is 97% identical to the S. enterica protein.


CorC of Salmonella typhimurium (P0A2L3)


DUF21-CBS-HlyC domain-containing protein of286 aas and 0 TMSs.

HlyC-like protein of Francisella tularensis


Hemolysin of 159 aas

Hemolysin of Treponema pallidum