title: Molecular Dissection of the Forces Responsible for Viral Capsid Assembly and Stabilization by Decoration Proteins.
abstract: Complex double-stranded DNA viruses utilize a terminase enzyme to package their genomes into a preassembled procapsid shell. DNA packaging triggers a major conformational change in the proteins assembled into the shell and most often subsequent addition of a decoration protein that is required to stabilize the structure. In bacteriophage λ, DNA packaging drives a procapsid expansion transition to afford a larger but fragile shell. The gpD decoration protein adds to the expanded shell as trimeric spikes at each of the 140 three-fold axes. The spikes provide mechanical strength to the shell such that it can withstand the tremendous internal forces generated by the packaged DNA in addition to environmental insults. Hydrophobic, electrostatic, and aromatic-proline noncovalent interactions have been proposed to mediate gpD trimer spike assembly at the expanded shell surface. Here, we directly examine each of these interactions and demonstrate that hydrophobic interactions play the dominant role. In the course of this study, we unexpectedly found that Trp308 in the λ major capsid protein (gpE) plays a critical role in shell assembly. The gpE-W308A mutation affords a soluble, natively folded protein that does not further assemble into a procapsid shell, despite the fact that it retains binding interactions with the scaffolding protein, the shell assembly chaparone protein. The data support a model in which the λ procapsid shell assembles via cooperative interaction of monomeric capsid proteins, as observed in the herpesviruses and phages such as P22. The significance of the results with respect to capsid assembly, maturation, and stability is discussed.
authors.affiliation: Department of Medicinal Chemistry, School of Pharmacy, University of Washington , Box 357610, Seattle, Washington 98195, United States.
authors.forename: Shannon
authors.initials: S
authors.lastname: Lambert
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado , Anschutz Medical Campus, Mail Stop C238, Aurora, Colorado 80045, United States.
authors.forename: Qin
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado , Anschutz Medical Campus, Mail Stop C238, Aurora, Colorado 80045, United States.
authors.forename: Rolando
authors.initials: R
authors.lastname: De Angeles
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado , Anschutz Medical Campus, Mail Stop C238, Aurora, Colorado 80045, United States.
authors.forename: Jenny R
authors.initials: JR
authors.lastname: Chang
authors.affiliation: Department of Biology, Macalester College , St. Paul, Minnesota 55105, United States.
authors.forename: Marcos
authors.initials: M
authors.lastname: Ortega
authors.affiliation: Program in Structural Biology and Biochemistry, University of Colorado , Anschutz Medical Campus, Mail Stop C290, Aurora, Colorado 80045, United States.
authors.forename: Christal
authors.initials: C
authors.lastname: Davis
authors.affiliation: Department of Medicinal Chemistry, School of Pharmacy, University of Washington , Box 357610, Seattle, Washington 98195, United States.
authors.forename: Carlos Enrique
authors.identifier: 0000-0003-2349-5758
authors.initials: CE
authors.lastname: Catalano
mesh_terms: D010582:Bacteriophage lambda / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D001696:Biomechanical Phenomena; D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D042003:DNA Packaging; D004279:DNA, Viral / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006023:Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D009154:Mutation; D000072417:Protein Domains; D017510:Protein Folding; D055503:Protein Multimerization; D011498:Protein Precursors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D055672:Static Electricity; D019065:Virus Assembly / Q000235:genetics*
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral; D006023:Glycoproteins; D011498:Protein Precursors; C406073:gpD protein, lambda phage