Structure and assembly of large, lipid-containing, dsDNA viruses
Abstract
My thesis work has involved 3D image reconstruction studies of several, very large icosahedral viruses. They are paramecium Chlorella virus type one (PBCV-1) (family Phycodnaviridae), Chilo iridescent virus (CIV) (family Iridoviridae), Frog Virus 3 (FV3) (family Iridoviridae), and Phaeocystis pouchetti virus (PpV01) (family not assigned). This study shows structural features of these large viruses at moderate resolution (∼2.6 nm) and reveals possible assembly principles that may serve as paradigms for other large icosahedral viruses. The image reconstruction and tilt experiments reveal that the PBCV-1 capsid shell (190 nm maximum diameter) consists of 12 pentamers and 1680 doughnut-like trimers arranged in a T = 169d skew icosahedral lattice. A lipid bilayer membrane closely follows the inner surface of the capsid. The capsid consists of 20 trisymmetrons (66 trimers each) and 12 pentasymmetrons (30 trimers plus one pentamer each) that are considered to be putative assembly intermediates. Image reconstruction shows that the CIV capsid (185 nm maximum diameter) consists of 12 pentamers and 1460 doughnut-like trimers (each trimer has a fiber that emanates from the center) arranged in a T = 147 icosahedral lattice. A lipid bilayer follows the inner side of the capsid. Like PBCV-1, the CIV capsid also consists of 20 trisymmetrons and 12 pentasymmetrons. However, in CIV, each trisymmetron contains 55 trimers. Image reconstruction shows that the FV3 capsid (190 nm maximum diameter) consists of a complex arrangement of thousands of knobs and ridges that represent one or more of the major capsid proteins. The complexity of the capsid organization has made it difficult to unambiguously establish the T-lattice symmetry from the current reconstruction. Currently, the T number appears to be either 147 or 148. A lipid bilayer membrane also lies just beneath the inner surface of the capsid. Image reconstruction shows that the PpV01 capsid (220 nm maximum diameter) consists of 2192 capsomers arranged in a T = 219 icosahedral lattice. Twelve capsomers occur as pentamers at the five-fold vertices and the remaining 2180 capsomers appear to be trimers. The PpV01 capsid consists of 20 trisymmetrons and 12 pentasymmetrons, with 91 trimers in each trisymmetron and 30 trimers in each pentasymmetron.
Degree
Ph.D.
Advisors
Baker, Purdue University.
Subject Area
Microbiology
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