A native MS based structural model of a dicistrovirus capsid

SNIJDER, J; UETRECHT, C; SANCHEZ- EUGENIA, R; MARTI G. A; AGUIRRE, J; GUERIN, D.M.A.; WUITE, G; ROOS, W; HECK, A

Simposio; Seventh International Virus Assembly Symposium; 2012

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Native Mass Spectrometry (MS) is a powerful tool in the structural characterisation of viral capsid assemblies. Here, we apply native MS to study the structure of a small RNA icosahedral virus capsid (T=1, p=3). First, determination of the capsid mass reveals that it is composed of 60 copies of each of the three capsid proteins (VP1/2/3). With a combined mass of 5366 kDa, this is the largest assembly ever for which an exact mass has been determined. Next, by studying the assembly intermediates of the capsid, we demonstrate that the penton composed of 5*VP1/2/3 is the fundamental structural unit of the capsid. By a combined tandem MS and Ion-mobility Spectrometry (IMS) analysis of this structural unit, we are able to resolve the interaction network within the penton and determine the topological arrangement of the subunits. We show that VP1 is the core subunit arranged along the 5-fold symmetry axis and that VP2/3 are situated along the penton-penton interface. By comparing the dissociation behaviour of the free penton to the intact capsid, we show that VP2 is crucial for the penton-penton interaction. Our native MS based structural model is in excellent agreement with the crystal structure of the capsid.