Molecular mechanism for ATP-dependent closure of the K+ channel Kir6.2

doi:10.1113/jphysiol.2003.048843

Molecular mechanism for ATP-dependent closure of the K⁺ channel Kir6.2

Scott A. John‡, James N. Weiss†‡, Lai-Hua Xie‡ and Bernard Ribalet†

*UCLA Cardiovascular Research Laboratory and the Departments of †Physiology and ‡Medicine (Cardiology) , UCLA School of Medicine, Los Angeles, CA 90095, USA

In the ATP-dependent K⁺ (K_ATP) 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 (P_o) 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 $beta$ phosphate group of ATP interacts with K185 to initiate closure, while the $alpha$ 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 $beta$ 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 $beta$ 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 $alpha$ 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 $beta$ phosphate group of ATP with K185 to destabilize the open state.

This article has been cited by other articles:

T. J. Craig, F. M. Ashcroft, and P. Proks
How ATP Inhibits the Open KATP Channel
J. Gen. Physiol., July 1, 2008; 132(1): 131 - 144.
[Abstract] [Full Text] [PDF]

L. Aguilar-Bryan and J. Bryan
Neonatal Diabetes Mellitus
Endocr. Rev., May 1, 2008; 29(3): 265 - 291.
[Abstract] [Full Text] [PDF]

K. Shimomura, C. A.J. Girard, P. Proks, J. Nazim, J. D. Lippiat, F. Cerutti, R. Lorini, S. Ellard, A. T. Hattersley, F. Barbetti, et al.
Mutations at the Same Residue (R50) of Kir6.2 (KCNJ11) That Cause Neonatal Diabetes Produce Different Functional Effects
Diabetes, June 1, 2006; 55(6): 1705 - 1712.
[Abstract] [Full Text] [PDF]

C.-W. Lin, Y.-W. Lin, F.-F. Yan, J. Casey, M. Kochhar, E. B. Pratt, and S.-L. Shyng
Kir6.2 Mutations Associated With Neonatal Diabetes Reduce Expression of ATP-Sensitive K+ channels: Implications in Disease Mechanism and Sulfonylurea Therapy
Diabetes, June 1, 2006; 55(6): 1738 - 1746.
[Abstract] [Full Text] [PDF]

B. Ribalet, S. A. John, L.-H. Xie, and J. N. Weiss
ATP-sensitive K+ channels: regulation of bursting by the sulphonylurea receptor, PIP2 and regions of Kir6.2
J. Physiol., March 1, 2006; 571(2): 303 - 317.
[Abstract] [Full Text] [PDF]

P. Tammaro, P. Proks, and F. M. Ashcroft
Functional effects of naturally occurring KCNJ11 mutations causing neonatal diabetes on cloned cardiac KATP channels
J. Physiol., February 15, 2006; 571(1): 3 - 14.
[Abstract] [Full Text] [PDF]

J. C. Koster, M. A. Permutt, and C. G. Nichols
Diabetes and Insulin Secretion: The ATP-Sensitive K+ Channel (KATP) Connection
Diabetes, November 1, 2005; 54(11): 3065 - 3072.
[Abstract] [Full Text] [PDF]

S. A John, J. N Weiss, and B. Ribalet
ATP sensitivity of ATP-sensitive K+ channels: role of the {gamma} phosphate group of ATP and the R50 residue of mouse Kir6.2
J. Physiol., November 1, 2005; 568(3): 931 - 940.
[Abstract] [Full Text] [PDF]

L. Li, X. Geng, M. Yonkunas, A. Su, E. Densmore, P. Tang, and P. Drain
Ligand-dependent Linkage of the ATP Site to Inhibition Gate Closure in the KATP Channel
J. Gen. Physiol., August 29, 2005; 126(3): 285 - 299.
[Abstract] [Full Text] [PDF]

T. Lu, M.-P. Hong, and H.-C. Lee
Molecular Determinants of Cardiac KATP Channel Activation by Epoxyeicosatrienoic Acids
J. Biol. Chem., May 13, 2005; 280(19): 19097 - 19104.
[Abstract] [Full Text] [PDF]

P. Proks, J. F. Antcliff, J. Lippiat, A. L. Gloyn, A. T. Hattersley, and F. M. Ashcroft
Molecular basis of Kir6.2 mutations associated with neonatal diabetes or neonatal diabetes plus neurological features
PNAS, December 14, 2004; 101(50): 17539 - 17544.
[Abstract] [Full Text] [PDF]

J. Bryan, W. H. Vila-Carriles, G. Zhao, A. P. Babenko, and L. Aguilar-Bryan
Toward Linking Structure With Function in ATP-Sensitive K+ Channels
Diabetes, December 1, 2004; 53(suppl_3): S104 - S112.
[Abstract] [Full Text] [PDF]

A. Tarasov, J. Dusonchet, and F. Ashcroft
Metabolic Regulation of the Pancreatic Beta-Cell ATP-Sensitive K+ Channel: A Pas de Deux
Diabetes, December 1, 2004; 53(suppl_3): S113 - S122.
[Abstract] [Full Text] [PDF]

T. Tsuboi, J. D. Lippiat, F. M. Ashcroft, and G. A. Rutter
ATP-dependent interaction of the cytosolic domains of the inwardly rectifying K+ channel Kir6.2 revealed by fluorescence resonance energy transfer
PNAS, January 6, 2004; 101(1): 76 - 81.
[Abstract] [Full Text] [PDF]