The Actin-Binding Interface of a Myosin III Is Phosphorylated in Vivo in Response to Signals from a Circadian Clock

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• 作者：Helene L. Cardasis ; Stanley M. Stevens Jr. ; Scott McClung ; Karen E. Kempler ; David H. Powell ; John R. Eyler ; Barbara-Anne Battelle
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：December 4, 2007
• 年：2007
• 卷：46
• 期：48
• 页码：13907 - 13919
• 全文大小：259K
• 年卷期：v.46,no.48(December 4, 2007)
• ISSN：1520-4995

文摘

Class III unconventional myosins are critical for the normal function of auditory hair cellsand the function and maintenance of photoreceptors; however, the roles of class III myosins in thesesensory cells are unknown. Class III myosins are unique in that they have a kinase domain at theirN-terminus; thus, they may have both signaling and motor functions. In the horseshoe crab Limuluspolyphemus, enhanced phosphorylation of an abundant, photoreceptor specific class III myosin at nightcorrelates with well-characterized circadian changes in photoreceptor structure and function. Thus, theLimulus visual system may be particularly useful for investigating the properties, modulation, and functionsof a class III myosin. Previously, we showed that two sites within the actin interface of full-length Limulusmyosin III expressed in baculovirus are substrates for both cyclic AMP-dependent protein kinase andautophosphorylation. In the current study, mass spectrometry was used to show that these same sites arephosphorylated in the endogenous protein extracted from Limulus lateral eye, and that enhancedphosphorylation at these sites occurs in vivo in response to natural circadian clock input to these eyes.These findings demonstrate in vivo changes in myosin III phosphorylation in response to a natural stimulus.This phosphorylation may modulate myosin III-actin interactions.