INVESTIGADORES
BOUZAT Cecilia Beatriz
artículos
Título:
Role of pairwise interactions between M1 and M2 domains of the nicotinic receptor in channel gating
Autor/es:
J CORRADI; GF SPITZMAUL; MJ DE ROSA; M COSTABEL; C BOUZAT
Revista:
BIOPHYSICAL JOURNAL
Editorial:
Biophysical Society USA
Referencias:
Año: 2007 vol. 92 p. 76 - 86
ISSN:
0006-3495
Resumen:
The adult form of the nicotinic receptor (AChR) consists of five subunits (a2bed), each having four transmembrane domains (M1-M4). The atomic model of the AChR shows that the pore-lining M2 domains make no extensive contacts with the rest of the transmembrane domains. However, there are several sites where close appositions between segments occur. It has been suggested that the pair aM1-F15Œ and aM2-L11Œ is one of the potential interactions between segments (1). To determine experimentally if these residues are interacting and to explore if this interhelical interaction is essential for channel gating, we combined mutagenesis with single-channel kinetic analysis. Mutations in aM1-F15Œ lead to profound changes in the opening rate and slighter changes in the closing rate. Channel gating is impaired as the volume of the residue increases. Rate-equilibrium linear free-energy relationship analysis reveals a ~70 % open-state like environment for aM1-F15Œ at the transition state of the gating reaction, suggesting that it moves early during the gating process. Replacing the residue at aM1-15Œ by that at aM2-11Œ and vice versa profoundly alters gating, but the combination of the two mutations restores gating to near normal, indicating that aM1-F15Œ and aM2-L11Œ are interchangeable. Double-mutant cycle analysis shows that these residues are energetically coupled. Thus, the interaction between M1 and M2 plays a key role in channel gating.