title: Secondary transport of metal-citrate complexes: the CitMHS family.
abstract: Primary and secondary transport of citrate has been extensively studied in pathogenic and non-pathogenic bacteria. Primary transporters of citrate complexed with metal ions, particularly Fe, have also garnered attention, with the fec system of E. coli being a classic example. In contrast, little is known about secondary transporters of metal-citrate complexes. Recently, a family of proteins responsible for secondary metal-citrate transport in bacteria was discovered and designated as the CitMHS transporter family. Several members have been functionally characterized to date and serve as the foundation for understanding this family. Three subfamilies have been categorized, depending on the main metal ion transported. These subfamilies are the Mg(2+)-citrate transporter, the Ca(2+)-citrate transporter, and the Fe(3+)-citrate transporter. Each subfamily is believed to be substrate-selective due to the metal-citrate complexes being abundantly present in their environment and/or the ability of the complex to be metabolized by the organism. The implication of this family in the pathogenic access to Fe, information about transcriptional control, putative structure, predicted family members, members characterized to date and potential use in bioremediation are discussed.
authors.affiliation: Department of Chemistry, Center for Science and Technology, Syracuse University, Syracuse, NY 13244-4100, USA.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Lensbouer
authors.forename: Robert P
authors.initials: RP
authors.lastname: Doyle
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D019343:Citric Acid / Q000737:chemistry / Q000378:metabolism*; D056831:Coordination Complexes / Q000737:chemistry / Q000378:metabolism; D006801:Humans
chemical_list: D002352:Carrier Proteins; D056831:Coordination Complexes; C020723:citrate-binding transport protein; D019343:Citric Acid