Characterization of proctolin binding sites on locust oviduct membranes
1992
Puiroux, J. | Pedelaborde, A. | Loughton, B.G.
The binding of [3H]proctolin to oviduct membranes has been analyzed to investigate the nature of proctolin binding sites in the oviduct. Proctolin binding was found to be time dependent, proportional to concentration of membrane protein, saturable, specific and reversible. Two apparent proctolin binding sites were recognized. The first had a Kd of 400 +/- 82 nM and a Bmax of 23.7 +/- 6.7 pmol/mg protein. The second had a Kd of 2.4 +/- 0.2 micromolar and a Bmax of 96.3 +/- 16.7 pmol/mg protein. Binding was specific in that competition experiments with a wide range of peptides showed that only Arg-Tyr-Leu-Pro-Ala was an effective competitor at micromolar concentrations. All other peptides examined weekly reduced proctolin binding at concentrations above 50 micromolar. Certain peptides were found to potentiate [3H]proctolin binding at low micromolar concentrations (1-10 micromolar) and to inhibit proctolin binding at higher concentrations. The significance of these findings is discussed.
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