3DET

Structure of the E148A, Y445A doubly ungated mutant of E.coli CLC_Ec1, Cl-/H+ antiporter

Summary for 3DET

• Entry DOI: 10.2210/pdb3det/pdb
• Related: 1OTS 1OTT 2HTK
• Descriptor: H(+)/Cl(-) exchange transporter clcA, Fab fragment, Heavy chain, Fab fragment, Light chain (3 entities in total)
• Functional Keywords: clc_ec1, antiporter, exchange-transporter, doubly ungated mutant, chloride, inner membrane, ion transport, membrane, stress response, transmembrane, membrane protein
• Biological source: Escherichia coli; More
• Cellular location: Cell inner membrane; Multi-pass membrane protein (Probable): P37019
• Total number of polymer chains: 6
• Total formula weight: 194045.27

Authors

Jayaram, H.,Accardi, A.,Wu, F.,Williams, C.,Miller, C. (deposition date: 2008-06-10, release date: 2008-06-17, Last modification date: 2024-10-09)

Primary citation

Jayaram, H.,Accardi, A.,Wu, F.,Williams, C.,Miller, C.
Ion permeation through a Cl--selective channel designed from a CLC Cl-/H+ exchanger
Proc.Natl.Acad.Sci.USA, 105:11194-11199, 2008

PubMed Abstract: The CLC family of Cl(-)-transporting proteins includes both Cl(-) channels and Cl(-)/H(+) exchange transporters. CLC-ec1, a structurally known bacterial homolog of the transporter subclass, exchanges two Cl(-) ions per proton with strict, obligatory stoichiometry. Point mutations at two residues, Glu(148) and Tyr(445), are known to impair H(+) movement while preserving Cl(-) transport. In the x-ray crystal structure of CLC-ec1, these residues form putative "gates" flanking an ion-binding region. In mutants with both of the gate-forming side chains reduced in size, H(+) transport is abolished, and unitary Cl(-) transport rates are greatly increased, well above values expected for transporter mechanisms. Cl(-) transport rates increase as side-chain volume at these positions is decreased. The crystal structure of a doubly ungated mutant shows a narrow conduit traversing the entire protein transmembrane width. These characteristics suggest that Cl(-) flux through uncoupled, ungated CLC-ec1 occurs via a channel-like electrodiffusion mechanism rather than an alternating-exposure conformational cycle that has been rendered proton-independent by the gate mutations.

PubMed: 18678918
DOI: 10.1073/pnas.0804503105

Experimental method

X-RAY DIFFRACTION (2.8 Å)