Jul 15, 1988

Characteristics of the binding of phenoxybenzamine to calmodulin

Biochemical Pharmacology
M Cimino, B Weiss


To determine the factors that influence the interaction between phenoxybenzamine and calmodulin, the binding of phenoxybenzamine to calmodulin was determined by equilibrium dialysis under a variety of experimental conditions. This interaction was found to be similar in some respects to the interaction between phenothiazines and calmodulin. It was saturable, with between 1 and 2 mol of phenoxybenzamine bound to 1 mol of calmodulin. It was also dependent upon temperature, the presence of a divalent cation such as calcium, and on pH, showing maximum binding at pH 6.5 with little binding at pH values below 4.2 or above 8.0. The site at which phenoxybenzamine bound to calmodulin appears to be similar to that at which certain antipsychotic agents bind, since several of them, including penfluridol, pimozide and spiroperidol, prevented the binding of phenoxybenzamine to calmodulin. However, in contrast to the reversible binding of most phenothiazines to calmodulin, phenoxybenzamine bound to calmodulin irreversibly. The binding of phenoxybenzamine to calmodulin was fairly selective in that other alpha-adrenergic agents such as prazosin, yohimbine and clonidine failed to bind to calmodulin when examined under the same experimental condit...Continue Reading

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Mentioned in this Paper

Phenoxybenzamine Hydrochloride
Plasma Protein Binding Capacity
Egtazic Acid Sodium Salt
Cyclic AMP-Phosphodiesterase Activator
Egtazic Acid Potassium Salt
Hydrogen-Ion Concentration

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