TY - JOUR
T1 - The energetic consequences of loop 9 gating motions in acetylcholine receptor-channels
AU - Jha, Archana
AU - Gupta, Shaweta
AU - Zucker, Shoshanna N.
AU - Auerbach, Anthony
PY - 2012/1
Y1 - 2012/1
N2 - Acetylcholine receptor-channels (AChRs) mediate fast synaptic transmission between nerve and muscle. In order to better-understand the mechanism by which this protein assembles and isomerizes between closed- and open-channel conformations we measured changes in the diliganded gating equilibrium constant (E 2) consequent to mutations of residues at the C-terminus of loop 9 (L9) in the α and e{open} subunits of mouse neuromuscular AChRs. These amino acids are close to two interesting interfaces, between the extracellular and transmembrane domain within a subunit (E-T interface) and between primary and complementary subunits (P-C interface). Most α subunit mutations modestly decreased E 2 (mainly by slowing the channel-opening rate constant) and sometimes produced AChRs that had heterogeneous gating kinetic properties. Mutations in the e{open} subunit had a larger effect and could either increase or decrease E 2, but did not induce kinetic heterogeneity. There are broad-but-weak energetic interactions between αL9 residues and others at the αE-T interface, as well as between the e{open}L9 residue and others at the P-C interface (in particular, the M2-M3 linker). These interactions serve, in part, to maintain the structural integrity of the AChR assembly at the E-T interface. Overall, the energy changes of L9 residues are significant but smaller than in other regions of the protein.
AB - Acetylcholine receptor-channels (AChRs) mediate fast synaptic transmission between nerve and muscle. In order to better-understand the mechanism by which this protein assembles and isomerizes between closed- and open-channel conformations we measured changes in the diliganded gating equilibrium constant (E 2) consequent to mutations of residues at the C-terminus of loop 9 (L9) in the α and e{open} subunits of mouse neuromuscular AChRs. These amino acids are close to two interesting interfaces, between the extracellular and transmembrane domain within a subunit (E-T interface) and between primary and complementary subunits (P-C interface). Most α subunit mutations modestly decreased E 2 (mainly by slowing the channel-opening rate constant) and sometimes produced AChRs that had heterogeneous gating kinetic properties. Mutations in the e{open} subunit had a larger effect and could either increase or decrease E 2, but did not induce kinetic heterogeneity. There are broad-but-weak energetic interactions between αL9 residues and others at the αE-T interface, as well as between the e{open}L9 residue and others at the P-C interface (in particular, the M2-M3 linker). These interactions serve, in part, to maintain the structural integrity of the AChR assembly at the E-T interface. Overall, the energy changes of L9 residues are significant but smaller than in other regions of the protein.
UR - http://www.scopus.com/inward/record.url?scp=84855162755&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84855162755&partnerID=8YFLogxK
U2 - 10.1113/jphysiol.2011.213892
DO - 10.1113/jphysiol.2011.213892
M3 - Article
C2 - 22025664
AN - SCOPUS:84855162755
SN - 0022-3751
VL - 590
SP - 119
EP - 129
JO - Journal of Physiology
JF - Journal of Physiology
IS - 1
ER -