title: Modulation of MICAL Monooxygenase Activity by its Calponin Homology Domain: Structural and Mechanistic Insights.
abstract: MICALs (Molecule Interacting with CasL) are conserved multidomain enzymes essential for cytoskeletal reorganization in nerve development, endocytosis, and apoptosis. In these enzymes, a type-2 calponin homology (CH) domain always follows an N-terminal monooxygenase (MO) domain. Although the CH domain is required for MICAL-1 cellular localization and actin-associated function, its contribution to the modulation of MICAL activity towards actin remains unclear. Here, we present the structure of a fragment of MICAL-1 containing the MO and the CH domains-determined by X-ray crystallography and small angle scattering-as well as kinetics experiments designed to probe the contribution of the CH domain to the actin-modification activity. Our results suggest that the CH domain, which is loosely connected to the MO domain by a flexible linker and is far away from the catalytic site, couples F-actin to the enhancement of redox activity of MICALMO-CH by a cooperative mechanism involving a trans interaction between adjacently bound molecules. Binding cooperativity is also observed in other proteins regulating actin assembly/disassembly dynamics, such as ADF/Cofilins.
authors.affiliation: Structural Enzymology and Thermodynamics Group, Department of Biophysics &Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe St., Baltimore, MD 21205, USA.
authors.forename: Saif S
authors.initials: SS
authors.lastname: Alqassim
authors.affiliation: Structural Enzymology and Thermodynamics Group, Department of Biophysics &Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe St., Baltimore, MD 21205, USA.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Urquiza
authors.affiliation: Structural Enzymology and Thermodynamics Group, Department of Biophysics &Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe St., Baltimore, MD 21205, USA.
authors.forename: Eitan
authors.initials: E
authors.lastname: Borgnia
authors.affiliation: Structural Enzymology and Thermodynamics Group, Department of Biophysics &Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe St., Baltimore, MD 21205, USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Nagib
authors.affiliation: Structural Enzymology and Thermodynamics Group, Department of Biophysics &Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe St., Baltimore, MD 21205, USA.
authors.forename: L Mario
authors.initials: LM
authors.lastname: Amzel
authors.affiliation: Department of Neurology and Department of Biophysics &Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe St., Baltimore, MD 21205, USA.|Structural Enzymology and Thermodynamics Group, Department of Biophysics &Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe St., Baltimore, MD 21205, USA.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Bianchet
mesh_terms: D000818:Animals; D018360:Crystallography, X-Ray; D051379:Mice; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000072417:Protein Domains; D013329:Structure-Activity Relationship
chemical_list: D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; C507541:Mical1 protein, mouse; D006899:Mixed Function Oxygenases