3q17

Structure of a slow CLC Cl-/H+ antiporter from a cyanobacterium in Bromide

spinqualitylabelsall models 3q17, resolution 3.60Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3q17 is a 2 chain structure with sequence from Aphanocapsa sp. (strain n-1). Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: BR Related: 3nd0 Gene: sll0855, syn:sll0855 (Aphanocapsa sp. (strain N-1)) Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed X-ray crystal structures have been previously determined for three CLC-type transporter homologues, but the absolute unitary transport rate is known for only one of these. The Escherichia coli Cl(-)/H(+) antiporter (EC) moves approximately 2000 Cl(-) ions/s, an exceptionally high rate among membrane-transport proteins. It is not known whether such rapid turnover is characteristic of ClCs in general or if the E. coli homologue represents a functional outlier. Here, we characterize a CLC Cl(-)/H(+) antiporter from the cyanobacterium Synechocystis sp. PCC6803 (SY) and determine its crystal structure at 3.2 A resolution. The structure of SY is nearly identical to that of EC, with all residues involved in Cl(-) binding and proton coupling structurally similar to their equivalents in EC. SY actively pumps protons into liposomes against a gradient and moves Cl(-) at approximately 20 s(-1), 1% of the EC rate. Electrostatic calculations, used to identify residues contributing to ion binding energetics in SY and EC, highlight two residues flanking the external binding site that are destabilizing for Cl(-) binding in SY and stabilizing in EC. Mutation of these two residues in SY to their counterparts in EC accelerates transport to approximately 150 s(-1), allowing measurement of Cl(-)/H(+) stoichiometry of 2/1. SY thus shares a similar structure and a common transport mechanism to EC, but it is by comparison slow, a result that refutes the idea that the transport mechanism of CLCs leads to intrinsically high rates. Structure of a Slow CLC Cl(-)/H(+) Antiporter from a Cyanobacterium.,Jayaram H, Robertson JL, Wu F, Williams C, Miller C Biochemistry. 2011 Jan 11. PMID:21174448 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

Proteopedia Page Contributors and Editors (what is this?)

OCA