Regulation Mechanism Of Calcineurin By RCAN1

Calcineurin(calcineurin,CN)is the only protein phosphatase in the S/T protein phosphatase family that is regulated by calcium ions and calmodulin,which plays a very important role in calcium signaling.CN is expressed in all organs of the human body and is involved in a variety of biological processes such as immune response,apoptosis,bone formation,muscle development,cardiovascular generation,and learning and memory.Clinically,CN is the target of immunosuppressive effects.The development of more specific CN inhibitors will bring good news to the majority of patients.Regulators of Calcineurin 1(RCAN1),a endogenous feedback regulator of CN signal transduction.Studying the regulator mechanism of RCAN1 on CN will provide ideas for the development of new drugs.In this paper,a combination of structural biology and enzyme kinetics were used to study the inhibition of CN phosphatase activity by RCAN1.We purified high-concentration,high-purity recombinant CN and RCAN1-4,C-terminal 57 residues of RCAN1-4 encoded by exon 7.Enzyme kinetics was used to determine the inhibition mechanism of CN by RCAN1-4.We found that RCAN1-4 and C-terminal exon7 fragments could not completely inhibit the phosphatase activity of CN even at saturated concentrations,and the inhibition of CN conforms to partial noncompetitive mechanism.When enzymes Enzymes form complexes with inhibitor,the substrates could still bind to the enzyme to form a ternary complex.The ternary complex of ESI has partial viability.To elucidate the interaction mode of CN and RCAN 1-4,we prepared the complex of CN and RCAN1-4,and carried out crystallization trials.However,only a few crystallites are currently obtained.