RT Journal Article
SR Electronic
T1 Functional Relationships between Agonist Binding Sites and Coupling Regions of Homomeric Cys-Loop Receptors
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 3662
OP 3669
DO 10.1523/JNEUROSCI.5940-10.2011
VO 31
IS 10
A1 Natalia Andersen
A1 Jeremías Corradi
A1 Mariana Bartos
A1 Steven M. Sine
A1 Cecilia Bouzat
YR 2011
UL http://www.jneurosci.org/content/31/10/3662.abstract
AB Each subunit in a homopentameric Cys-loop receptor contains a specialized coupling region positioned between the agonist binding domain and the ion conductive channel. To determine the contribution of each coupling region to the stability of the open channel, we constructed a receptor subunit (α7-5-HT3A) with both a disabled coupling region and a reporter mutation that alters unitary conductance, and coexpressed normal and mutant subunits. The resulting receptors show single-channel current amplitudes that are quantized according to the number of reporter mutations per receptor, allowing correlation of the number of intact coupling regions with mean open time. We find that each coupling region contributes an equal increment to the stability of the open channel. However, by altering the numbers and locations of active coupling regions and binding sites, we find that a coupling region in a subunit flanked by inactive binding sites can still stabilize the open channel. We also determine minimal requirements for channel opening regardless of stability and find that channel opening can occur in a receptor with one active coupling region flanked by functional binding sites or with one active binding site flanked by functional coupling regions. The overall findings show that, whereas the agonist binding sites contribute interdependently and asymmetrically to open-channel stability, the coupling regions contribute independently and symmetrically.