Heparin binding induces conformational changes in Adeno-associated virus serotype 2.
Adeno-associated virus serotype 2 (AAV2) uses heparan sulfate proteoglycan as a cell surface-attachment receptor. In this study the structures of AAV2 alone and complexed with heparin were determined to approximately 18A resolution using cryo-electron microscopy and three-dimensional image reconstruction. A difference map showed positive density, modeled as heparin, close to the icosahedral twofold axes and between the protrusions that surround the threefold axes of the capsid. Regions of the model near the threefold place the receptor in close proximity to basic residues previously identified as part of the heparin binding site. The region of the model near the twofold axes identifies a second contact site, not previously characterized but which is also possibly configured by heparin binding. The difference map also revealed two significant conformational changes: (I) at the tops of the threefold protrusions, which have become flattened in the complex, and (II) at the fivefold axes where the top of the channel is widened possibly in response to movement of the HI loops in the capsid proteins. Ordered density in the interior of the capsid in the AAV2-heparin complex was interpreted as nucleic acid, consistent with the presence of non-viral DNA in the expressed capsids.
Levy
Hazel C
HC
Department of Biochemistry and Molecular Biology, Center for Structural Biology, The McKnight Brain Institute, College of Medicine, 1600 SW Archer Road, P.O. Box 100245, University of Florida, Gainesville, FL 32610, USA.
Bowman
Valorie D
VD
Govindasamy
Lakshmanan
L
McKenna
Robert
R
Nash
Kevin
K
Warrington
Kenneth
K
Chen
Weijun
W
Muzyczka
Nicholas
N
Yan
Xiaodong
X
Baker
Timothy S
TS
Agbandje-McKenna
Mavis
M
D002213:Capsid / Q000737:chemistry; D036022:Capsid Proteins / Q000737:chemistry; D020285:Cryoelectron Microscopy; D000229:Dependovirus / Q000737:chemistry*; D006493:Heparin / Q000737:chemistry*; D007091:Image Processing, Computer-Assisted; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D019251:Nucleocapsid / Q000737:chemistry; D011487:Protein Conformation; D014771:Virion / Q000737:chemistry
D036022:Capsid Proteins; C442558:VP3 protein, Dependovirus; D006493:Heparin