Copper homeostasis protein CutC was originally thought to be involved in copper tolerance in Escherichia coli, as mutation in the corresponding gene lead to an increased copper sensitivity [1]. However, this phenotype has been later reported to depend on the levels of he mRNA-interfering complementary RNA regulator MicL, which is transcribed from a promoter located within the coding sequence of the cutC gene in enterobacteria [2]. In the plant pathogen Xylella fastidiosa, this protein has been reported as specific for copper efflux [3]. The structure of this protein in the bacteria Shigella flexneri showed a monomer structure that adopts a common TIM beta/alpha barrel with eight beta strands surrounded by eight alpha-helices [4]. The human homologue of this protein, whose structure showed a potential copper-binding site, has an important role in intracellular copper homeostasis [5,6].

1: Identification of cutC and cutF (nlpE) genes involved in copper tolerance in Escherichia coli. Gupta SD, Lee BT, Camakaris J, Wu HC; J Bacteriol 1995;177:4207-4215. PMID:7635807

2: MicL, a new sigmaE-dependent sRNA, combats envelope stress by repressing synthesis of Lpp, the major outer membrane lipoprotein. Guo MS, Updegrove TB, Gogol EB, Shabalina SA, Gross CA, Storz G; Genes Dev. 2014;28:1620-1634. PMID:25030700

3: Overexpression of mqsR in Xylella fastidiosa Leads to a Priming Effect of Cells to Copper Stress Tolerance. Carvalho IGB, Merfa MV, Teixeira-Silva NS, Martins PMM, Takita MA, de Souza AA; Front Microbiol. 2021;12:712564. PMID:34616378

4: Crystal structure of the copper homeostasis protein (CutCm) from Shigella flexneri at 1.7 A resolution: the first structure of a new sequence family of TIM barrels. Zhu DY, Zhu YQ, Huang RH, Xiang Y, Yang N, Lu HX, Li GP, Jin Q, Wang DC; Proteins. 2005;58:764-768. PMID:15624211

5: Crystal structure of human copper homeostasis protein CutC reveals a potential copper-binding site. Li Y, Du J, Zhang P, Ding J; J Struct Biol. 2010;169:399-405. PMID:19878721

6: Silencing of Human CutC Gene (hCutC) Induces Apoptosis in HepG2 Cells. Kunjunni R, Sathianathan S, Behari M, Chattopadhyay P, Subbiah V; Biol Trace Elem Res. 2016;172:120-126. PMID:26660891