Binding of intracellular Ca 21 ions to troponin C subsequent to membrane excitation triggers the interaction of actin with myosin molecules by displacing the inhibition induced by troponin I at diastolic levels of [Ca]i. Therefore, in intact myocardial cells, the amplitude and rate of tension development and relaxation are primarily determined by the rate of Ca mobilization and deprivation, by ...

Within the family of serotonin receptors, the 5-hydroxytryptamine-3 (5-HT3) receptor is the only ligand-gated ion channel. It is composed of five subunits, of which the 5-HT3A and 5-HT3B subunits are best characterized. Several studies, however, have reported on the functional diversity of native 5-HT3 receptors, which cannot solely be explained on the basis of the 5-HT3A and 5-HT3B subunits. A...

Measurements and observations of five early events of fertilization, singly and in pairs, from single sea urchin eggs have revealed the precise temporal sequence and spatial distribution of these events. In the Arbacia punctulata egg, a wave of surface contraction occurs coincident with membrane depolarization (t = 0). These two earliest events are followed by the onset of a rapid, propagated i...

Odorant-dependent behaviors in insects are triggered by the binding of odorant ligands to variable subunits heteromeric olfactory receptors. Previous studies have shown, however, that specific odor ORco, common subunit receptor heteromers, may allosterically alter function and profoundly affect subsequent behavioral responses. Using an insect cell–based screening platform, we identified charact...

Sensory systems define an animal's capacity for perception and can evolve to promote survival in new environmental niches. We have uncovered a noncanonical mechanism for sweet taste perception that evolved in hummingbirds since their divergence from insectivorous swifts, their closest relatives. We observed the widespread absence in birds of an essential subunit (T1R2) of the only known vertebr...