title: Distinct Morphology of Human T-Cell Leukemia Virus Type 1-Like Particles.
abstract: The Gag polyprotein is the main retroviral structural protein and is essential for the assembly and release of virus particles. In this study, we have analyzed the morphology and Gag stoichiometry of human T-cell leukemia virus type 1 (HTLV-1)-like particles and authentic, mature HTLV-1 particles by using cryogenic transmission electron microscopy (cryo-TEM) and scanning transmission electron microscopy (STEM). HTLV-1-like particles mimicked the morphology of immature authentic HTLV-1 virions. Importantly, we have observed for the first time that the morphology of these virus-like particles (VLPs) has the unique local feature of a flat Gag lattice that does not follow the curvature of the viral membrane, resulting in an enlarged distance between the Gag lattice and the viral membrane. Other morphological features that have been previously observed with other retroviruses include: (1) a Gag lattice with multiple discontinuities; (2) membrane regions associated with the Gag lattice that exhibited a string of bead-like densities at the inner leaflet; and (3) an arrangement of the Gag lattice resembling a railroad track. Measurement of the average size and mass of VLPs and authentic HTLV-1 particles suggested a consistent range of size and Gag copy numbers in these two groups of particles. The unique local flat Gag lattice morphological feature observed suggests that HTLV-1 Gag could be arranged in a lattice structure that is distinct from that of other retroviruses characterized to date.
authors.affiliation: Institute for Molecular Virology &amp; DDS-PhD Dual Degree Program, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA. jmaldo@umn.edu.
authors.forename: José O
authors.initials: JO
authors.lastname: Maldonado
authors.affiliation: Institute for Molecular Virology, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA. caosheng@wh.iov.cn.
authors.forename: Sheng
authors.initials: S
authors.lastname: Cao
authors.affiliation: Institute for Molecular Virology &amp; Characterization Facility, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA. zhangwei@umn.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Institute for Molecular Virology, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA. mansky@umn.edu.
authors.forename: Louis M
authors.initials: LM
authors.lastname: Mansky
mesh_terms: D020285:Cryoelectron Microscopy; D015683:Gene Products, gag / Q000032:analysis; D015368:Human T-lymphotropic virus 1 / Q000737:chemistry / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D014771:Virion / Q000737:chemistry / Q000648:ultrastructure*
chemical_list: D015683:Gene Products, gag
keywords: deltaretrovirus; lentivirus; virus assembly