title: High-resolution structure of the catalytic region of MICAL (molecule interacting with CasL), a multidomain flavoenzyme-signaling molecule.
abstract: Semaphorins are extracellular cell guidance cues that govern cytoskeletal dynamics during neuronal and vascular development. MICAL (molecule interacting with CasL) is a multidomain cytosolic protein with a putative flavoprotein monooxygenase (MO) region required for semaphorin-plexin repulsive axon guidance. Here, we report the 1.45-A resolution crystal structure of the FAD-containing MO domain of mouse MICAL-1 (residues 1-489). The topology most closely resembles that of the NADPH-dependent flavoenzyme p-hydroxybenzoate hydroxylase (PHBH). Comparison of structures before and after reaction with NADPH reveals that, as in PHBH, the flavin ring can switch between two discrete positions. In contrast with other MOs, this conformational switch is coupled with the opening of a channel to the active site, suggestive of a protein substrate. In support of this hypothesis, distinctive structural features highlight putative protein-binding sites in suitable proximity to the active site entrance. The unusual juxtaposition of this N-terminal MO (hydroxylase) activity with the characteristics of a multiprotein-binding scaffold exhibited by the C-terminal portion of the MICALs represents a unique combination of functionality to mediate signaling.
authors.affiliation: Cancer Research UK Receptor Structure Research Group, Division of Structural Biology, University of Oxford, UK.
authors.forename: Christian
authors.initials: C
authors.lastname: Siebold
authors.forename: Nick
authors.initials: N
authors.lastname: Berrow
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Walter
authors.forename: Karl
authors.initials: K
authors.lastname: Harlos
authors.forename: Ray J
authors.initials: RJ
authors.lastname: Owens
authors.forename: David I
authors.initials: DI
authors.lastname: Stuart
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Terman
authors.forename: Alex L
authors.initials: AL
authors.lastname: Kolodkin
authors.forename: R Jeroen
authors.initials: RJ
authors.lastname: Pasterkamp
authors.forename: E Yvonne
authors.initials: EY
authors.lastname: Jones
mesh_terms: D000818:Animals; D001665:Binding Sites; D020134:Catalytic Domain; D003460:Crystallization; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005415:Flavins / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D011487:Protein Conformation; D015398:Signal Transduction
chemical_list: D005415:Flavins; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D005182:Flavin-Adenine Dinucleotide; D009249:NADP; C507541:Mical1 protein, mouse; D006899:Mixed Function Oxygenases