Two Salt Bridges Differentially Contribute to the Maintenance of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Channel Function |
| |
Authors: | Guiying Cui Cody S. Freeman Taylor Knotts Chengyu Z. Prince Christopher Kuang Nael A. McCarty |
| |
Affiliation: | From the Division of Pulmonology, Allergy/Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis Research, Emory University School of Medicine and Children''s Healthcare of Atlanta, Atlanta, Georgia 30322 |
| |
Abstract: | Previous studies have identified two salt bridges in human CFTR chloride ion channels, Arg352-Asp993 and Arg347-Asp924, that are required for normal channel function. In the present study, we determined how the two salt bridges cooperate to maintain the open pore architecture of CFTR. Our data suggest that Arg347 not only interacts with Asp924 but also interacts with Asp993. The tripartite interaction Arg347-Asp924-Asp993 mainly contributes to maintaining a stable s2 open subconductance state. The Arg352-Asp993 salt bridge, in contrast, is involved in stabilizing both the s2 and full (f) open conductance states, with the main contribution being to the f state. The s1 subconductance state does not require either salt bridge. In confirmation of the role of Arg352 and Asp993, channels bearing cysteines at these sites could be latched into a full open state using the bifunctional cross-linker 1,2-ethanediyl bismethanethiosulfonate, but only when applied in the open state. Channels remained latched open even after washout of ATP. The results suggest that these interacting residues contribute differently to stabilizing the open pore in different phases of the gating cycle. |
| |
Keywords: | ABC Transporter CFTR Gating Oocyte Xenopus MTS Reagents Pore Salt Bridge |
|
|