Three-dimensional organization of retroviral capsid proteins on a lipid monolayer.
We have used a method for the two-dimensional crystallization of retroviral structural proteins to obtain a three-dimensional structure of negatively stained, membrane-bound, histidine-tagged Moloney murine leukemia virus (M-MuLV) capsid protein (his-MoCA) arrays. Tilted and untilted micrographs from crystals formed by purified his-MoCA proteins incubated beneath lipid monolayers containing nickel-chelating lipids were used in 3D reconstructions. The 2D crystals had unit cell dimensions of a=72.6 A, b=72.5 A and gamma=119.5 degrees, but appeared to have no intrinsic symmetry (p1) in 3D, in contrast to the trigonal or hexagonal appearance of their 2D projections. Membrane-bound his-MoCA proteins showed a strand-like organization, apparently with dimer building blocks. Membrane-proximal regions, or putative N-terminal domains (NTDs), dimerized with different partners than the membrane-distal putative C-terminal domains (CTDs). Evidence also suggests that CTDs can adopt alternate orientations relative to their NTDs, forming interstrand connections. Our results are consistent with helical-spiral models for retrovirus particle assembly, but are not easily reconcilable with icosahedral models.
McDermott
J
J
Vollum Institute and Department of Microbiology, Oregon Health Sciences University, Portland, OR 97201-3098, USA.
Mayo
K
K
Barklis
E
E
D002213:Capsid / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure*; D002614:Chelating Agents / Q000378:metabolism; D003460:Crystallization; D019281:Dimerization; D008563:Membrane Lipids / Q000378:metabolism*; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D008979:Moloney murine leukemia virus / Q000737:chemistry / Q000648:ultrastructure*; D009532:Nickel / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure
D002614:Chelating Agents; D008563:Membrane Lipids; D008567:Membranes, Artificial; D011993:Recombinant Fusion Proteins; D009532:Nickel