BINDING-PROTEIN FROM RAT NERVE

  • 1 January 1977
    • journal article
    • research article
    • Vol. 9  (3) , 227-240
Abstract
Leucine bound competitively to a soluble protein (MW 97,000 daltons) from rat sciatic nerve under certain experimental conditions to form a high MW aggregate (MW > 302,000). Kinetic study showed that the equilibrium constant for leucine-binding is 1.33 .times. 104 l/m and the rate constants for binding and unbinding are k1 = 0.424 l/m per s and k-1 = 3.18 .times. 10-5/s, respectively. The binding reaction was accompanied by an endothermic enthalpy change of 5000 cal/mol and the favorable equilibrium appeared to be due to the large positive (35.3 eu [entropy units]) entropy of binding. L-Proline, thymidine and succinic acid also bound, non-competitively with leucine, to proteins in the same fraction. Binding of those compounds and leucine was enhanced by the presence of Mg2+. Rat muscle and plasma proteins did not significantly bind leucine under these experimental conditions. The presence of this binding protein in rat nerve suggests an additional mechanism in the metabolism and in the transport of amino acids for incorporation into a protein structure in nerve.

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