PDBsum entry 3ow7

Go to PDB code: 
protein metals Protein-protein interface(s) links
Transport protein PDB id
Jmol PyMol
Protein chains
296 a.a. *
CU1 ×4
* Residue conservation analysis
PDB id:
Name: Transport protein
Title: Crystal structure of the membrane fusion protein cusb from e coli.
Structure: Cation efflux system protein cusb. Chain: a, b. Synonym: membrane fusion protein. Engineered: yes
Source: Escherichia coli. Organism_taxid: 83333. Strain: k12. Gene: cusb, ylcd, b0574, jw0563. Expressed in: escherichia coli. Expression_system_taxid: 562
3.78Å     R-factor:   0.282     R-free:   0.324
Authors: C.-C.Su
Key ref:
C.C.Su et al. (2009). Crystal structure of the membrane fusion protein CusB from Escherichia coli. J Mol Biol, 393, 342-355. PubMed id: 19695261 DOI: 10.1016/j.jmb.2009.08.029
17-Sep-10     Release date:   17-Nov-10    
Supersedes: 3h9t
Go to PROCHECK summary

Protein chains
Pfam   ArchSchema ?
P77239  (CUSB_ECOLI) -  Cation efflux system protein CusB
407 a.a.
296 a.a.
Key:    PfamA domain  Secondary structure  CATH domain

 Gene Ontology (GO) functional annotation 
  GO annot!
  Cellular component     membrane   1 term 
  Biological process     transmembrane transport   1 term 


DOI no: 10.1016/j.jmb.2009.08.029 J Mol Biol 393:342-355 (2009)
PubMed id: 19695261  
Crystal structure of the membrane fusion protein CusB from Escherichia coli.
C.C.Su, F.Yang, F.Long, D.Reyon, M.D.Routh, D.W.Kuo, A.K.Mokhtari, J.D.Van Ornam, K.L.Rabe, J.A.Hoy, Y.J.Lee, K.R.Rajashankar, E.W.Yu.
Gram-negative bacteria, such as Escherichia coli, frequently utilize tripartite efflux complexes belonging to the resistance-nodulation-division family to expel diverse toxic compounds from the cell. These systems contain a periplasmic membrane fusion protein (MFP) that is critical for substrate transport. We here present the x-ray structures of the CusB MFP from the copper/silver efflux system of E. coli. This is the first structure of any MFPs associated with heavy-metal efflux transporters. CusB bridges the inner-membrane efflux pump CusA and outer-membrane channel CusC to mediate resistance to Cu(+) and Ag(+) ions. Two distinct structures of the elongated molecules of CusB were found in the asymmetric unit of a single crystal, which suggests the flexible nature of this protein. Each protomer of CusB can be divided into four different domains, whereby the first three domains are mostly beta-strands and the last domain adopts an entirely helical architecture. Unlike other known structures of MFPs, the alpha-helical domain of CusB is folded into a three-helix bundle. This three-helix bundle presumably interacts with the periplasmic domain of CusC. The N- and C-termini of CusB form the first beta-strand domain, which is found to interact with the periplasmic domain of the CusA efflux pump. Atomic details of how this efflux protein binds Cu(+) and Ag(+) were revealed by the crystals of the CusB-Cu(I) and CusB-Ag(I) complexes. The structures indicate that CusB consists of multiple binding sites for these metal ions. These findings reveal novel structural features of an MFP in the resistance-nodulation-division efflux system and provide direct evidence that this protein specifically interacts with transported substrates.
  Selected figure(s)  
Figure 3.
Fig. 3. Structural comparison of the MFPs. (a) Superimposition of the crystal structures of CusB (orange) and MexA (purple). (b) Superimposition of Domain 1 of CusB (orange) with the membrane-proximal domain of MexA (purple). (c) Superimposition of Domain 2 of CusB (orange) with the β-barrel domain of MexA (purple). (d) Superimposition of Domain 3 of CusB (orange) with the lipoyl domain of MexA (purple).
Figure 5.
Fig. 5. Cu^+- and Ag^+-binding sites of molecule A of CusB. Cu^+ and Ag^+ ions are represented by purple and green spheres, respectively. The overall locations of sites C1, C2, and A1 are circled. Anomalous difference Fourier maps are contoured at 4.6 σ, 4.0 σ, and 4.2 σ for sites C1, C2, and A1, respectively. Anomalous peak heights for sites C1′, C2′, and A1′ in molecule B of CusB (not shown) were found to be 4.6 σ, 4.6 σ, and 5.4 σ, respectively.
  The above figures are reprinted by permission from Elsevier: J Mol Biol (2009, 393, 342-355) copyright 2009.  
  Figures were selected by an automated process.  

Literature references that cite this PDB file's key reference

  PubMed id Reference
20981744 C.C.Su, F.Long, and E.W.Yu (2011).
The Cus efflux system removes toxic ions via a methionine shuttle.
  Protein Sci, 20, 6.  
21350490 C.C.Su, F.Long, M.T.Zimmermann, K.R.Rajashankar, R.L.Jernigan, and E.W.Yu (2011).
Crystal structure of the CusBA heavy-metal efflux complex of Escherichia coli.
  Nature, 470, 558-562.
PDB code: 3ne5
21210186 D.Raimunda, M.González-Guerrero, B.W.Leeber, and J.M.Argüello (2011).
The transport mechanism of bacterial Cu(+)-ATPases: distinct efflux rates adapted to different function.
  Biometals, 24, 467-475.  
21249122 R.Kulathila, R.Kulathila, M.Indic, and B.van den Berg (2011).
Crystal structure of Escherichia coli CusC, the outer membrane component of a heavy metal efflux pump.
  PLoS One, 6, e15610.
PDB code: 3pik
21221942 B.Y.Yun, Y.Xu, S.Piao, N.Kim, J.H.Yoon, H.S.Cho, K.Lee, and N.C.Ha (2010).
Periplasmic domain of CusA in an Escherichia coli Cu+/Ag+ transporter has metal binding sites.
  J Microbiol, 48, 829-835.  
20442961 E.H.Kim, C.Rensing, and M.M.McEvoy (2010).
Chaperone-mediated copper handling in the periplasm.
  Nat Prod Rep, 27, 711-719.  
20534468 F.De Angelis, J.K.Lee, J.D.O'Connell, L.J.Miercke, K.H.Verschueren, V.Srinivasan, C.Bauvois, C.Govaerts, R.A.Robbins, J.M.Ruysschaert, R.M.Stroud, and G.Vandenbussche (2010).
Metal-induced conformational changes in ZneB suggest an active role of membrane fusion proteins in efflux resistance systems.
  Proc Natl Acad Sci U S A, 107, 11038-11043.
PDB code: 3lnn
20865003 F.Long, C.C.Su, M.T.Zimmermann, S.E.Boyken, K.R.Rajashankar, R.L.Jernigan, and E.W.Yu (2010).
Crystal structures of the CusA efflux pump suggest methionine-mediated metal transport.
  Nature, 467, 484-488.
PDB codes: 3k07 3kso 3kss
The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time. Where a reference describes a PDB structure, the PDB code is shown on the right.