PDBsum entry 3ooc

Transport protein

PDB id: 3ooc

Contents

Protein chains

297 a.a. *

* Residue conservation analysis

PDB id:

3ooc

Name:

Transport protein

Title:

Crystal structure of the membrane fusion protein cusb from escherichia 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

Resolution:

3.40Å R-factor: 0.264 R-free: 0.318

Authors:

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

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

Date:

30-Aug-10 Release date: 29-Dec-10

Supersedes:

3h9i

Protein chains

P77239  (CUSB_ECOLI) -  Cation efflux system protein CusB from Escherichia coli (strain K12)

Seq: 407 a.a.

Struc: 297 a.a.

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.

ABSTRACT

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.