title: Adeno-associated virus-2 and its primary cellular receptor--Cryo-EM structure of a heparin complex.
abstract: Adeno-associated virus serotype 2 (AAV-2) is a leading candidate vector for gene therapy. Cell entry starts with attachment to a primary receptor, Heparan Sulfate Proteoglycan (HSPG) before binding to a co-receptor. Here, cryo-electron microscopy provides direct visualization of the virus-HSPG interactions. Single particle analysis was performed on AAV-2 complexed with a 17 kDa heparin fragment at 8.3 A resolution. Heparin density covers the shoulder of spikes surrounding viral 3-fold symmetry axes. Previously implicated, positively charged residues R(448/585), R(451/588) and R(350/487) from another subunit cluster at the center of the heparin footprint. The footprint is much more extensive than apparent through mutagenesis, including R(347/484), K(395/532) and K(390/527) that are more conserved, but whose roles have been controversial. It also includes much of a region proposed as a co-receptor site, because prior studies had not revealed heparin interactions. Heparin density bridges over the viral 3-fold axes, indicating multi-valent attachment to symmetry-related binding sites.
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: O'Donnell
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Taylor
authors.forename: Michael S
authors.initials: MS
authors.lastname: Chapman
mesh_terms: D002213:Capsid / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism / Q000821:virology*; D020285:Cryoelectron Microscopy; D000229:Dependovirus / Q000737:chemistry* / Q000648:ultrastructure*; D006367:HeLa Cells; D019812:Heparan Sulfate Proteoglycans / Q000737:chemistry / Q000378:metabolism*; D006493:Heparin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000648:ultrastructure; D011991:Receptors, Virus / Q000235:genetics / Q000378:metabolism*
chemical_list: D019812:Heparan Sulfate Proteoglycans; D011956:Receptors, Cell Surface; D011991:Receptors, Virus; C037680:heparin receptor; D006493:Heparin