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Probing the Role of Backbone Hydrogen Bonding in a Critical β Sheet of the Extracellular Domain of a Cys‐Loop Receptor
Author(s) -
Gleitsman Kristin R.,
Lester Henry A.,
Dougherty Dennis A.
Publication year - 2009
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.200900092
Subject(s) - beta sheet , nicotinic acetylcholine receptor , gating , biophysics , hydrogen bond , cys loop receptors , torpedo , chemistry , receptor , acetylcholine receptor , ion channel , protein structure , nicotinic agonist , alpha 4 beta 2 nicotinic receptor , stereochemistry , biochemistry , biology , molecule , organic chemistry
Probing the sheet : The network of hydrogen bonds formed in the outer β sheet of the nicotinic acetylcholine receptor (nAChR; see figure) is fairly robust and tolerates single amide‐to‐ester mutations throughout. However, eliminating two proximal hydrogen bonds completely destroys receptor function; this adds further support to gating models that ascribe important roles to these β strands of the nAChR extracellular domain.Long‐range communication is essential for the function of members of the Cys‐loop family of neurotransmitter‐gated ion channels. The involvement of the peptide backbone in binding‐induced conformational changes that lead to channel gating in these membrane proteins is an interesting, but unresolved issue. To probe the role of the peptide backbone, we incorporated a series of α‐hydroxy acid analogues into the β‐sheet‐rich extracellular domain of the muscle subtype of the nicotinic acetylcholine receptor, the prototypical Cys‐loop receptor. Specifically, mutations were made in β strands 7 and 10 of the α subunit. A number of single backbone mutations in this region were well tolerated. However, simultaneous introduction of two proximal backbone mutations led to surface‐expressed, nonfunctional receptors. Together, these data suggest that while the receptor is remarkably robust in its ability to tolerate single amide‐to‐ester mutations throughout these β strands, more substantial perturbations to this region have a profound effect on the protein. These results support a model in which backbone movements in the outer β sheet are important for receptor function.