PDBsum entry 2h2p

Ion transport

PDB id: 2h2p

Contents

Protein chains

444 a.a. *

221 a.a. *

211 a.a. *

Metals

SEK ×8

* Residue conservation analysis

PDB id:

2h2p

Name:

Ion transport

Title:

Crystal structure of clc-ec1 in complex with fab fragment in secn-

Structure:

Clc cl transporter. Chain: a, b. Synonym: clc-ec1. H(+)/cl(-) exchange transporter clca. Engineered: yes. Fab fragment, heavy chain. Chain: c, e. Fab fragment, light chain. Chain: d, f

Source:

Escherichia coli. Organism_taxid: 562. Gene: clca, eric. Expressed in: escherichia coli. Expression_system_taxid: 562. Mus musculus. House mouse. Organism_taxid: 10090. Cell_line: hybridoma cell line.

Biol. unit:

Hexamer (from PQS)

Resolution:

3.10Å R-factor: 0.278 R-free: 0.280

Authors:

W.Nguitragool,C.Miller

Key ref:

W.Nguitragool and C.Miller (2006). Uncoupling of a CLC Cl-/H+ exchange transporter by polyatomic anions. J Mol Biol, 362, 682-690. PubMed id: 16905147 DOI: 10.1016/j.jmb.2006.07.006

Date:

19-May-06 Release date: 30-May-06

Protein chains

P37019  (CLCA_ECOLI) -  H(+)/Cl(-) exchange transporter ClcA from Escherichia coli (strain K12)

Seq: 473 a.a.

Struc: 444 a.a.

Protein chains

Q4VBH1  (Q4VBH1_RAT) -  Ighg protein from Rattus norvegicus

Seq: 467 a.a.

Struc: 221 a.a.*

Protein chains

No UniProt id for this chain

Struc: 211 a.a.

* PDB and UniProt seqs differ at 60 residue positions (black crosses)

DOI no: 10.1016/j.jmb.2006.07.006

J Mol Biol 362:682-690 (2006)

PubMed id: 16905147

Uncoupling of a CLC Cl-/H+ exchange transporter by polyatomic anions.

W.Nguitragool, C.Miller.

ABSTRACT

CLC-ec1 is a bacterial archetype of CLC transporters, a ubiquitous class of proteins that catalyze transmembrane exchange of Cl- and H+ necessary for pH regulation of numerous physiological processes. Despite a profusion of high-resolution structures, the molecular mechanism of exchange remains unknown. Here, we rigorously demonstrate strict exchange stoichiometry of 2 Cl-/1 H+. In addition to Cl- and Br-, two non-halide ions, NO3- and SCN-, are shown to be transported by CLC-ec1, but with reduced H+ counter-transport. The loss of proton coupling to these anions is accompanied by an absence of bound anions in the central and external Cl- binding sites in the protein's anion selectivity region, as revealed by crystallographic comparison of Br- and SeCN- bound to this region.

Selected figure(s)

Figure 4.
Figure 4. Structure of CLC-ec1. This ribbon representation of the homodimeric protein, viewed from the membrane plane (extracellular side above, cytoplasmic side below), emphasizes the anion-binding region. The inner and central chloride ions are shown as green spheres, and the external glutamate (E148) is indicated as a red sphere positioned at one of the carboxylate oxygen atoms. An expanded representation of this region is shown below, as viewed from the dimer interface, with the three anion-binding sites indicated.

Figure 5.
Figure 5. Anion-binding region of CLC-ec1 in Br^− and SeCN^−. Crystals of (a) and (b) wild-type CLC-ec1 and (c) and (d) E148A mutant were grown in (a) and (c) Br^− or (b)and (d) SeCN^−, and structures were determined to 3.1–3.4 Å. Shown here is the anion-binding region, with anion-coordinating side-chains Glu(Ala)148, Ser107, and Tyr445 indicated. Anomalous difference maps for Br^− (green) or SeCN^− (red) were calculated and contoured at 4 σ. For E148A in Br^−-the three anion-binding sites (external, central, and inner) are shown by anomalous density; in this dataset, inner-site binding is weak. Not shown here are additional loci of anomalous Se density at the aqueous surfaces of the transporter; these are probably of no functional significance, since Br^− is never seen here. PDB accession number for wild-type in SeCN^− 2H2P; for E148A in SeCN^− 2H2S.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2006, 362, 682-690) copyright 2006.

Figures were selected by an automated process.