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2.A.6.1.4
Cu+ /Ag+ efflux pump, CusABCF (may pump ions from the periplasm to the external medium); CusF is a periplasmic Cu+ /Ag+ binding receptor essential for full resistance (Franke et al., 2003). Bagai et al. (2007) reported that CusB (MFP) binds one molecule of Ag+ or Cu+ via four conserved methionines and induces a substrate-linked conformational change (Bagai et al., 2007). The crystal structures of CusB are available (Su et al., 2009). The crystal structure of the CusAB complex has been solved (PDB# 3K07) (Su et al., 2011a). CusC is listed under TC# 1.B.17.3.5. The metal-binding methionines play a role in restricting the substrates to monovalent heavy metals (Conroy et al., 2010). It has been reported to export L-cysteine (Yamada et al., 2006). Crystal structures of the CusA efflux pump suggested that methionine residues in a 3-methionine cluster, bind the metal as a transport intermediate (Long et al., 2010). Four methionine pairs in the transmembrane region, and one in the periplasmic domain may comprise the channel. Cu+ is exported from the cytoplasm to the periplasmic chaparone, CusF in the extracellular space (Padilla-Benavides et al. 2014). The Cus efflux system removes Cu+ and Ag+ from both the cell cytoplasm and the periplasm (Su et al., 2011b; Delmar et al. 2014). Metal-bound CusB is required for activation of Cu+ transfer from CusF directly to a site in the CusA antiporter (Chacón et al. 2014). Metal transfer occurs between CusF and apo-CusB, and when metal-loaded, CusB plays a role in the regulation of metal ion transfer from CusF to CusA in the periplasm.  The ratio of CusA (RND):CusB (MFP):CusC (OMF) is 3:6:3 (Delmar et al. 2013). Intermediates in metal transfer reactions have been measured (Chacón et al. 2018).

Accession Number:P77214
Protein Name:CusF aka CusX
Length:110
Molecular Weight:12251.00
Species:Escherichia coli [83333]
Location1 / Topology2 / Orientation3: Periplasm1
Substrate Cu+, Ag+

Cross database links:

Genevestigator: P77214
EchoBASE: EB3985
EcoGene: EG14234
eggNOG: COG5569
HEGENOM: HBG648484
DIP: DIP-9350N
RefSeq: AP_001218.1    NP_415105.1   
Entrez Gene ID: 945188   
Pfam: PF11604   
BioCyc: EcoCyc:G6321-MONOMER    ECOL168927:B0573-MONOMER   
KEGG: ecj:JW0562    eco:b0573   

Gene Ontology

GO:0042597 C:periplasmic space
GO:0005507 F:copper ion binding
GO:0005375 F:copper ion transmembrane transporter activity
GO:0016530 F:metallochaperone activity
GO:0005515 F:protein binding
GO:0006878 P:cellular copper ion homeostasis
GO:0060003 P:copper ion export
GO:0010273 P:detoxification of copper ion
GO:0015679 P:plasma membrane copper ion transport
GO:0010272 P:response to silver ion
GO:0010043 P:response to zinc ion

References (6)

[1] “A 718-kb DNA sequence of the Escherichia coli K-12 genome corresponding to the 12.7-28.0 min region on the linkage map.”  Oshima T.et.al.   8905232
[2] “The complete genome sequence of Escherichia coli K-12.”  Blattner F.R.et.al.   9278503
[3] “Highly accurate genome sequences of Escherichia coli K-12 strains MG1655 and W3110.”  Hayashi K.et.al.   16738553
[4] “Molecular analysis of the copper-transporting efflux system CusCFBA of Escherichia coli.”  Franke S.et.al.   12813074
[5] “The independent cue and cus systems confer copper tolerance during aerobic and anaerobic growth in Escherichia coli.”  Outten F.W.et.al.   11399769
[6] “The product of the ybdE gene of the Escherichia coli chromosome is involved in detoxification of silver ions.”  Franke S.et.al.   11283292
Structure:
1ZEQ   2QCP   2VB2   2VB3   3E6Z     

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FASTA formatted sequence
1:	MKKALQVAMF SLFTVIGFNA QANEHHHETM SEAQPQVISA TGVVKGIDLE SKKITIHHDP 
61:	IAAVNWPEMT MRFTITPQTK MSEIKTGDKV AFNFVQQGNL SLLQDIKVSQ