Structural mechanism of SDS-induced enzyme activity of scorpion hemocyanin revealed by electron cryomicroscopy.
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.
Cong
Yao
Y
National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA.
Zhang
Qinfen
Q
Woolford
David
D
Schweikardt
Thorsten
T
Khant
Htet
H
Dougherty
Matthew
M
Ludtke
Steven J
SJ
Chiu
Wah
W
Decker
Heinz
H
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*
D021122:Protein Subunits; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate; D006433:Hemocyanins; D014442:Monophenol Monooxygenase