title: Structural mechanism of SDS-induced enzyme activity of scorpion hemocyanin revealed by electron cryomicroscopy.
abstract: Phenoloxidases (POs) occur in all organisms and are involved in skin and hair coloring in mammals, and initiating melanization in wound healing. Mutation or overexpression of PO can cause albinism or melanoma, respectively. SDS can convert inactive PO and the oxygen carrier hemocyanin (Hc) into enzymatically active PO. Here we present single-particle cryo-EM maps at subnanometer resolution and pseudoatomic models of the 24-oligomeric Hc from scorpion Pandinus imperator in resting and SDS-activated states. Our structural analyses led to a plausible mechanism of Hc enzyme PO activation: upon SDS activation, the intrinsically flexible Hc domain I twists away from domains II and III in each subunit, exposing the entrance to the active site; this movement is stabilized by enhanced interhexamer and interdodecamer interactions, particularly in the central linker subunits. This mechanism could be applicable to other type 3 copper proteins, as the active site is highly conserved.
authors.affiliation: National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Yao
authors.initials: Y
authors.lastname: Cong
authors.forename: Qinfen
authors.initials: Q
authors.lastname: Zhang
authors.forename: David
authors.initials: D
authors.lastname: Woolford
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schweikardt
authors.forename: Htet
authors.initials: H
authors.lastname: Khant
authors.forename: Matthew
authors.initials: M
authors.lastname: Dougherty
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Ludtke
authors.forename: Wah
authors.initials: W
authors.lastname: Chiu
authors.forename: Heinz
authors.initials: H
authors.lastname: Decker
mesh_terms: D000818:Animals; D001665:Binding Sites; D020134:Catalytic Domain; D020285:Cryoelectron Microscopy; D004789:Enzyme Activation; D006433:Hemocyanins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D014442:Monophenol Monooxygenase / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012605:Scorpions / Q000378:metabolism*; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology*; D013501:Surface-Active Agents / Q000494:pharmacology*
chemical_list: D021122:Protein Subunits; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate; D006433:Hemocyanins; D014442:Monophenol Monooxygenase