title: Atomic force microscopy and electron microscopy analysis of retrovirus Gag proteins assembled in vitro on lipid bilayers.
abstract: We have used an in vitro system that mimics the assembly of immature Moloney murine leukemia virus (M-MuLV) particles to examine how viral structural (Gag) proteins oligomerize at membrane interfaces. Ordered arrays of histidine-tagged Moloney capsid protein (his-MoCA) were obtained on membrane bilayers composed of phosphatidylcholine (PC) and the nickel-chelating lipid 1, 2-di-O-hexadecyl-sn-glycero-3-(1'-2"-R-hydroxy-3'N-(5-amino-1-carboxy pentyl)iminodiacetic acid)propyl ether (DHGN). The membrane-bound arrays were analyzed by electron microscopy (EM) and atomic force microscopy (AFM). Two-dimensional projection images obtained by EM showed that bilayer-bound his-MoCA proteins formed cages surrounding different types of protein-free cage holes with similar cage holes spaced at 81.5-A distances and distances between dissimilar cage holes of 45.5 A. AFM images, showing topological features viewed near the membrane-proximal domain of the his-MoCA protein, revealed a cage network of only symmetrical hexamers spaced at 79-A distances. These results are consistent with a model in which dimers constitute structural building blocks and where membrane-proximal and distal his-MoCA regions interact with different partners in membrane-bound arrays.
authors.affiliation: Vollum Institute, Department of Microbiology, Oregon Health Sciences University, Portland, Oregon 97201-3098 USA.
authors.forename: G
authors.initials: G
authors.lastname: Zuber
authors.forename: E
authors.initials: E
authors.lastname: Barklis
mesh_terms: D002213:Capsid / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D003001:Cloning, Molecular; D004926:Escherichia coli; D015683:Gene Products, gag / Q000378:metabolism* / Q000648:ultrastructure*; D008051:Lipid Bilayers / Q000737:chemistry*; D018625:Microscopy, Atomic Force / Q000379:methods; D008854:Microscopy, Electron / Q000379:methods; D008979:Moloney murine leukemia virus / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000737:chemistry*; D011994:Recombinant Proteins / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D015683:Gene Products, gag; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D011994:Recombinant Proteins