ZnuA includes periplasmic solute binding proteins such as TroA that interacts with an ATP-binding cassette transport system in Treponema pallidum [1]. ZnuA is part of the bacterial zinc-uptake complex ZnuABC, whose components are the following families, ZinT, Pfam:PF09223, Pfam:PF00950, Pfam:PF00005, all of which are regulated by the transcription-regulator family FUR, Pfam:PF01475. ZinT acts as a Zn2+-buffering protein that delivers Zn2+ to ZnuA (TroA), a high-affinity zinc-uptake protein. In Gram-negative bacteria the ZnuABC transporter system ensures an adequate import of zinc in Zn2+-poor environments, such as those encountered by pathogens within the infected host [2,3].

1: Treponema pallidum TroA is a periplasmic zinc-binding protein with a helical backbone. Lee YH, Deka RK, Norgard MV, Radolf JD, Hasemann CA; Nat Struct Biol 1999;6:628-633. PMID:10404217

2: Role of ZnuABC and ZinT in Escherichia coli O157:H7 zinc acquisition and interaction with epithelial cells. Gabbianelli R, Scotti R, Ammendola S, Petrarca P, Nicolini L, Battistoni A; BMC Microbiol. 2011;11:36. PMID:21338480

3: The Salmonella enterica ZinT structure, zinc affinity and interaction with the high-affinity uptake protein ZnuA provide insight into the management of periplasmic zinc. Ilari A, Alaleona F, Tria G, Petrarca P, Battistoni A, Zamparelli C, Verzili D, Falconi M, Chiancone E; Biochim Biophys Acta. 2014;1840:535-544. PMID:24128931