title: Heparin binding induces conformational changes in Adeno-associated virus serotype 2.
abstract: 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.
authors.affiliation: 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.
authors.forename: Hazel C
authors.initials: HC
authors.lastname: Levy
authors.forename: Valorie D
authors.initials: VD
authors.lastname: Bowman
authors.forename: Lakshmanan
authors.initials: L
authors.lastname: Govindasamy
authors.forename: Robert
authors.initials: R
authors.lastname: McKenna
authors.forename: Kevin
authors.initials: K
authors.lastname: Nash
authors.forename: Kenneth
authors.initials: K
authors.lastname: Warrington
authors.forename: Weijun
authors.initials: W
authors.lastname: Chen
authors.forename: Nicholas
authors.initials: N
authors.lastname: Muzyczka
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Yan
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Baker
authors.forename: Mavis
authors.initials: M
authors.lastname: Agbandje-McKenna
mesh_terms: 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
chemical_list: D036022:Capsid Proteins; C442558:VP3 protein, Dependovirus; D006493:Heparin