This family represents a bacterial outer membrane lipoprotein that is necessary for signalling by the Cpx pathway [1]. This pathway responds to cell envelope disturbances and increases the expression of periplasmic protein folding and degradation factors. While the molecular function of the NlpE protein is unknown, it may be involved in detecting bacterial adhesion to abiotic surfaces. In Escherichia coli and Salmonella typhi, NlpE is also known to confer copper tolerance in copper-sensitive strains of Escherichia coli, and may be involved in copper efflux and delivery of copper to copper-dependent enzymes [2]. This domain is found at the C-terminus of the NlpE protein [3].

1: Surface sensing and adhesion of Escherichia coli controlled by the Cpx-signaling pathway. Otto K, Silhavy TJ; Proc Natl Acad Sci U S A 2002;99:2287-2292. PMID:11830644

2: 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

3: Structural studies of the Cpx pathway activator NlpE on the outer membrane of Escherichia coli. Hirano Y, Hossain MM, Takeda K, Tokuda H, Miki K; Structure. 2007;15:963-976. PMID:17698001