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CitMHS family

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Family of transport proteins

The Citrate-Mg:H (CitM) / Citrate-Ca:H (CitH) Symporter (CitMHS) Family (TC# 2.A.11) is a family of transport proteins belonging to the Ion transporter superfamily. Members of this family are found in Gram-positive and Gram-negative bacteria, archaea and possibly eukaryotes. These proteins all probably arose by an internal gene duplication event. Lensbouer & Doyle (2010) have reviewed these systems, classifying the porters with three superfamilies, according to ion-preference:

1) Mg-preferring,

2) Ca-preferring, and

3) Fe-preferring.

A representative list of proteins belonging to the CitMHS family can be found in the Transporter Classification Database.

CitM and CitH

Two of the characterized members of the CitMHS family, both citrate uptake permeases from Bacillus subtilis, are CitM (TC# 2.A.11.1.1) and CitH (TC# 2.A.11.1.2).

Function

CitM is believed to transport a citrate-Mgcomplex in symport with one H per Mg-citrate while CitH apparently transports a citrate-Ca complex in symport with protons. The cation specificity of CitM is: Mg, Mn, Ba, Ni, Co, Ca and Zn, in this preferential order. CitM is highly specific for citrate and D-isocitrate and does not transport other di- and tri-carboxylates including succinate, L-isocitrate, cis-aconitate and tricarballylate. For CitH, the cation specificity (in order of preference) is: Ca, Ba and Sr. The two proteins are 60% identical, contain about 400 amino acyl residues and possess twelve putative transmembrane spanners. A CitM homologue in S. mutans transports citrate conjugated to Fe or Mn but not Ca, Mg or Ni.

The transport reactions catalyzed by (1) CitM and (2) CitH, respectively, are:

(1) Citrate • Mg (out) + nH (out) ⇌ Citrate • Mg (in) + nH (in)

(2) Citrate (out) + nH (out) ⇌ Citrate (in) + nH (in)

(3) Citrate • Ca (out) + nH (out) ⇌ Citrate • Ca (in) + nH (in)

See also

References

  1. Prakash, Shraddha; Cooper, Garret; Singhi, Soumya; Saier, Milton H. (2003-12-03). "The ion transporter superfamily". Biochimica et Biophysica Acta (BBA) - Biomembranes. 1618 (1): 79–92. doi:10.1016/j.bbamem.2003.10.010. ISSN 0006-3002. PMID 14643936.
  2. Lensbouer, Joshua J.; Patel, Ami; Sirianni, Joseph P.; Doyle, Robert P. (2008-08-01). "Functional characterization and metal ion specificity of the metal-citrate complex transporter from Streptomyces coelicolor". Journal of Bacteriology. 190 (16): 5616–5623. doi:10.1128/JB.00456-08. ISSN 1098-5530. PMC 2519374. PMID 18556792.
  3. "2.A.11. The Citrate-Mg2+:H+ (CitM) Citrate-Ca2+:H+ (CitH) Symporter (CitMHS) Family". Transporter Classification Database. Retrieved 2016-03-04.
  4. Boorsma, A.; van der Rest, M. E.; Lolkema, J. S.; Konings, W. N. (1996-11-01). "Secondary transporters for citrate and the Mg(2+)-citrate complex in Bacillus subtilis are homologous proteins". Journal of Bacteriology. 178 (21): 6216–6222. doi:10.1128/jb.178.21.6216-6222.1996. ISSN 0021-9193. PMC 178492. PMID 8892821.
  5. ^ Krom, B. P.; Warner, J. B.; Konings, W. N.; Lolkema, J. S. (2000-11-01). "Complementary metal ion specificity of the metal-citrate transporters CitM and CitH of Bacillus subtilis". Journal of Bacteriology. 182 (22): 6374–6381. doi:10.1128/jb.182.22.6374-6381.2000. ISSN 0021-9193. PMC 94783. PMID 11053381.
  6. Li, H.; Pajor, A. M. (2002-01-01). "Functional characterization of CitM, the Mg2+-citrate transporter". The Journal of Membrane Biology. 185 (1): 9–16. doi:10.1007/s00232-001-0106-1. ISSN 0022-2631. PMID 11891560. S2CID 8677932.
  7. Warner, Jessica B.; Lolkema, Juke S. (2002-11-01). "Growth of Bacillus subtilis on citrate and isocitrate is supported by the Mg2+-citrate transporter CitM". Microbiology. 148 (Pt 11): 3405–3412. doi:10.1099/00221287-148-11-3405. ISSN 1350-0872. PMID 12427932.
  8. Korithoski, Bryan; Krastel, Kirsten; Cvitkovitch, Dennis G. (2005-07-01). "Transport and metabolism of citrate by Streptococcus mutans". Journal of Bacteriology. 187 (13): 4451–4456. doi:10.1128/JB.187.13.4451-4456.2005. ISSN 0021-9193. PMC 1151779. PMID 15968054.
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As of 9 March 2016, this article is derived in whole or in part from Transporter Classification Database. The copyright holder has licensed the content in a manner that permits reuse under CC BY-SA 3.0 and GFDL. All relevant terms must be followed. The original text was at "The Citrate-Mg2+:H+ (CitM) Citrate-Ca2+:H+ (CitH) Symporter (CitMHS) Family"

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