title: Auto-inhibitory effects of an IQ motif on protein structure and function.
abstract: The denuded IQ2 domain, i.e. myosin heavy chain not associated with regulatory light chains, exerts an inhibitory effect on myosin ATPase activity. In this study, we elaborated a structural explanation for this auto-inhibitory effect of IQ2 on myosin function. We employed analytical ultracentrifugation, circular dichroism, and surface plasmon resonance spectroscopy to investigate structural and functional properties of a myosin heavy chain (MYH) head-rod fragment aa664-915. MYH(664-915) was monomeric, adopted a closed shape, and bound essential myosin light chains (HIS-MLC-1) with low affinity to IQ1. Deletion of IQ2, however opened MYH(664-915). Four amino acids present in IQ2 could be identified to be responsible for this auto-inhibitory structural effect: alanine mutagenesis of I814, Q815, R819, and W827 stretched MYH(664-915) and increased 30-fold the binding affinity of HIS-MLC-1 to IQ1. In this study we show, that denuded IQ2 favours a closed conformation of myosin with a low HIS-MLC-1 binding affinity. The collapsed structure of myosin with denuded IQ2 could explain the auto-inhibitory effects of IQ2 on enzymatic activity of myosin.
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, Department of Molecular Muscle Physiology, Robert-Rössle-Strasse 10, 13125 Berlin, Germany. petzhold@mdc-berlin.de
authors.forename: Daria
authors.initials: D
authors.lastname: Petzhold
authors.forename: Janine
authors.initials: J
authors.lastname: Lossie
authors.forename: Joachim
authors.initials: J
authors.lastname: Behlke
authors.forename: Sandro
authors.initials: S
authors.lastname: Keller
authors.forename: Hannelore
authors.initials: H
authors.lastname: Haase
authors.forename: Ingo
authors.initials: I
authors.lastname: Morano
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors*; D000818:Animals; D002942:Circular Dichroism; D018995:Myosin Heavy Chains / Q000737:chemistry* / Q000235:genetics; D018994:Myosin Light Chains / Q000737:chemistry; D024462:Myosin Type II / Q000037:antagonists & inhibitors*; D017434:Protein Structure, Tertiary / Q000235:genetics; D051381:Rats; D017384:Sequence Deletion; D020349:Surface Plasmon Resonance; D014461:Ultracentrifugation
chemical_list: D018994:Myosin Light Chains; D000251:Adenosine Triphosphatases; D024462:Myosin Type II; D018995:Myosin Heavy Chains