The collaboration between research groups at the University of Zurich (Prof. Urs Greber), Centro Nacional de Biotecnología (Dr. Carmen San Martín) and IFIMAC (Dr. Pedro J. de Pablo) have discovered the role of the core protein V in the stability and biomechanics of individual human adenovirus (Ad5) particles. Ad5 is an icosahedral virus capsid that packs the genome (dsDNA) toguether with three type of proteins to form the core. Out of these proteins, protein V is believed to connect the inner capsid surface to the outer genome layer. Here we explored the mechanical properties and in vitro mechanical disassembly of particles lacking protein V (Ad5-ΔV). Ad5-ΔV particles were softer and less brittle than the wildtype ones (Ad5-wt), but they were more prone to release pentons (proteins located at the icosahedral vertexes) under mechanical fatigue. In Ad5-ΔV, dsDNA did not readily diffuse out of cracked capsids, and the core appeared more condensed than in Ad5-wt. These observations suggest that pV antagonizes the condensing role of the other core proteins. Protein V provides mechanical reinforcement, and facilitates genome release by keeping DNA connected to capsid fragments that detach during the disruption of the virus. This scenario is in line with the location of protein V in the virion and its role in Ad5 cell entry during infection. [Full article]
