Smooth muscle α-actinin binds tightly to fesselin and attenuates its activity toward actin polymerization
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Fesselin is an actin binding protein from smooth muscle that nucleates actin polymerization in a Ca++-calmodulin dependent manner, bundles actin and inhibits the actin-activated ATPase activity of myosin S1. We now report that fesselin binds to smooth muscle α-actinin. Binding was measured by blot overlay, affinity chromatography and sedimentation methods. Binding was moderate with an association constant of 1–4×107 M−1 assuming a 1:1 association of fesselin with α-actinin. Fesselin binds to the central spectrin domain repeat region of α-actinin but not to the CH1–CH2 domain. Fesselin accelerates the polymerization of actin. This activity of fesselin was attenuated by α-actinin. These observations support the role of fesselin in organizing the cytoskeleton.
KeywordsActin Polymerization Bundle Actin Pyrenyl Calponin Homology Domain Spectrin Repeat
The authors thank Dr. Roberto Dominguez for his gift of the CH1–CH2 domain of α-actinin and Ms. Natalie Lonergan and Ms. Tamatha Baxley for technical assistance. This work was supported by grant AR35216 from the National Institutes of Health to JMC.
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