The identification of taurine receptors from rat heart sarcolemma

Two sets of taurine receptors on rat heart sarcolemma have been identified. The high affinity taurine receptors (Kd=3.5×10 −4M) show a non-cooperative binding profile while the low affinity taurine receptors exhibit positive cooperativity. Taurine binding to the membrane exhibits a typical bell shaped pH profile with maximum binding occurring at pH 8.0. The maximum temperature for binding is 24°C. The effect of various taurine analogues on the receptors was investigated. It was found that binding is prevented by hypotaurine and inhibited to a lesser degree by isethionic acid and cysteine sulfinic acid, while β-alanine was found to increase taurine binding. The effect of several hydrolytic enzymes was also examined and it was shown that several proteases and phospholipase C inhibit binding. The results indicate that the taurine receptors are membrane bound proteins in a phospholipid environment.