tailieunhanh - Báo cáo khoa học: Betaine protects urea-induced denaturation of myosin subfragment-1

We have demonstrated previously that urea inhibits the activity and alters the tertiary structure of skeletal muscle myosin in a biphasic manner. This was attributed to differential effects on its globular and filamentous por-tion. | ễFEBS Journal Betaine protects urea-induced denaturation of myosin subfragment-1 Susana Ortiz-Costa1 2 Martha M. Sorenson2 and Mauro Sola-Penna1 1 Laboratorio de Enzimologia e Controle do Metabolismo Departamento de Farmacos Universidade Federaldo Rio de Janeiro Brazil 2 Instituto de Bioquimica Medica Universidade Federaldo Rio de Janeiro Brazil Keywords methylamine muscle myosin protection urea Correspondence M. Sola-Penna Laboratorio de Enzimologia e Controle do Metabolismo LabECoM Departamento de Farmacos Faculdade de Farmacia Universidade Federaldo Rio de Janeiro Ilha do Fundao Rio de Janeiro -RJ 21941-590 Brazil Fax Tel 55 21 2260 9192 ext 251 E-mail maurosp@ Received 30 January 2008 revised 19 March 2008 accepted 30 April 2008 doi We have demonstrated previously that urea inhibits the activity and alters the tertiary structure of skeletal muscle myosin in a biphasic manner. This was attributed to differential effects on its globular and filamentous portion. The inhibition of catalytic activity was counteracted by methylamines. With the aim of comprehending the effects of urea on the catalytic globular portion of myosin this study examines the effects of urea and the countereffects of betaine on the catalytic activity and structure of myosin subfragment-1. It is shown that urea inactivates subfragment-1 in parallel with its ability to induce exposure of the enzyme hydrophobic domains as assessed using intrinsic and extrinsic fluorescence. Both effects are counteracted by betaine which alone does not significantly affect subfragment-1. Urea also enhances the accessibility of thiol groups promotes aggregation and decreases the a-helix content of S1 effects that are also counteracted by betaine. We conclude that urea-induced inactivation of the enzyme is caused by partial unfolding of the myosin catalytic domain. Osmolytes are osmotically active solutes that can be grouped into four major classes polyols sugar and sugar .

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