Conformational state-dependent anion binding in prestin: evidence for allosteric modulation.
Outer hair cells boost auditory performance in mammals. This amplification relies on an expansive array of intramembranous molecular motors, identified as prestin, that drive somatic electromotility. By measuring nonlinear capacitance, the electrical signature of electromotility, we are able to assess prestin's conformational state and interrogate the effectiveness of anions on prestin's activity. We find that the affinity of anions depends on the state of prestin that we set with a variety of perturbations (in membrane tension, temperature, and voltage), and that movement into the expanded state reduces the affinity of prestin for anions. These data signify that anions work allosterically on prestin. Consequently, anions are released from prestin's binding site during expansion, i.e., during hyperpolarization. This is at odds with the extrinsic voltage sensor model, which suggests that prestin-bound intracellular anions are propelled deep into the membrane. Furthermore, we hypothesize that prestin's susceptibility to many biophysical forces, and notably its piezoelectric nature, may reflect anion interactions with the motor.
Department of Surgery (Otolaryngology), Yale University School of Medicine, New Haven, Connecticut, USA.
Lei
L
Song
Joseph
J
Santos-Sacchi
D000494:Allosteric Regulation; D000818:Animals; D000838:Anions / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D002491:Central Nervous System Agents / Q000737:chemistry / Q000494:pharmacology; D002712:Chlorides / Q000737:chemistry; D025802:Electric Capacitance; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology; D020128:Inhibitory Concentration 50; D008564:Membrane Potentials; D008959:Models, Neurological; D017711:Nonlinear Dynamics; D018408:Patch-Clamp Techniques; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D012459:Salicylates / Q000737:chemistry / Q000494:pharmacology; D013696:Temperature
D000838:Anions; D002491:Central Nervous System Agents; D002712:Chlorides; C498722:Pres protein, Cavia porcellus; D011506:Proteins; D012459:Salicylates