Molecular Mechanism for ATP‐Dependent Closure of the K+ Channel Kir6.2
Open Access
- 1 October 2003
- journal article
- Published by Wiley in The Journal of Physiology
- Vol. 552 (1) , 23-34
- https://doi.org/10.1113/jphysiol.2003.048843
Abstract
In the ATP‐dependent K+ (KATP) channel pore‐forming protein Kir6.2, mutation of three positively charged residues, R50, K185 and R201, impairs the ability of ATP to close the channel. The mutations do not change the channel open probability (Po) in the absence of ATP, supporting the involvement of these residues in ATP binding. We recently proposed that at least two of these positively charged residues, K185 and R201, interact with ATP phosphate groups to cause channel closure: the β phosphate group of ATP interacts with K185 to initiate closure, while the α phosphate interacts with R201 to stabilize the channel's closed state. In the present study we replaced these three positive residues with residues of different charge, size and hydropathy. For K185 and R201, we found that charge, more than any other property, controls the interaction of ATP with Kir6.2. At these positions, replacement with another positive residue had minor effects on ATP sensitivity. In contrast, replacement of K185 with a negative residue (K185D/E) decreased ATP sensitivity much more than neutral substitutions, suggesting that an electrostatic interaction between the β phosphate group of ATP and K185 destabilizes the open state of the channel. At R201, replacement with a negative charge (R201E) had multiple effects, decreasing ATP sensitivity and preventing full channel closure at high concentrations. In contrast, the R50E mutation had a modest effect on ATP sensitivity, and only residues such as proline and glycine that affect protein structure caused major decreases in ATP sensitivity at the R50 position. Based on these results and the recently published structure of Kir3.1 cytoplasmic domain, we propose a scheme where binding of the β phosphate group of ATP to K185 induces a motion of the surrounding region, which destabilizes the open state, favouring closure of the M2 gate. Binding of the α phosphate group of ATP to R201 then stabilizes the closed state. R50 on the N‐terminus controls ATP binding by facilitating the interaction of the β phosphate group of ATP with K185 to destabilize the open state.Keywords
This publication has 13 references indexed in Scilit:
- Structural Basis of Inward RectificationCell, 2002
- Rotational movement during cyclic nucleotide-gated channel openingNature, 2001
- Structural Determinants of Pip2 Regulation of Inward Rectifier KATP ChannelsThe Journal of general physiology, 2000
- Involvement of the N‐terminus of Kir6.2 in the inhibition of the KATP channel by ATPThe Journal of Physiology, 1999
- K ATP channel inhibition by ATP requires distinct functional domains of the cytoplasmic C terminus of the pore-forming subunitProceedings of the National Academy of Sciences, 1998
- The sulphonylurea receptor SUR1 regulates ATP‐sensitive mouse Kir6.2 K+ channels linked to the green fluorescent protein in human embryonic kidney cells (HEK 293)The Journal of Physiology, 1998
- Molecular determinants of KATP channel inhibition by ATPThe EMBO Journal, 1998
- SWISS‐MODEL and the Swiss‐Pdb Viewer: An environment for comparative protein modelingElectrophoresis, 1997
- A new generation of information retrieval tools for biologists: the example of the ExPASy WWW serverTrends in Biochemical Sciences, 1994
- A simple method for displaying the hydropathic character of a proteinJournal of Molecular Biology, 1982