Wednesday Colloquia

How does a simple virus self-assemble

by Prof. Vinothan N. Manoharan (Harvard University, USA.)

Wednesday, December 12, 2018 from to (Asia/Kolkata)
at Lecture Theatre ( AG-66 )
TIFR
Description
Simple RNA viruses consist of proteins that form a highly-ordered protective shell (called a capsid) around the viral RNA. Many such viruses are self-assembled: infectious viral particles can form spontaneously in a mixture of RNA and coat protein in a buffer, in the absence of any host factors.  We do not yet understand how this self-assembly process results in such highly ordered shells. The yield and fidelity of the assembly is particularly remarkable in viruses with a triangulation number of 3 or higher, in which case some of the proteins must find their way to 5-fold coordinated sites and others to 6-fold coordinated sites on the same shell. To understand how such systems assemble, we have developed an interferometric technique that allows us to measure the scattering of individual assembling viral particles (MS2 bacteriophage) on time scales ranging from 1 ms to 1000s. By comparing the scattered intensity to that of the wild-type virus, we infer the mass of proteins that have attached to the central RNA as a function of time. We find that individual particles grow to nearly full size in a short time following a much longer delay period. The distribution of delay times suggests that the assembly follows a nucleation-and-growth pathway.  I will discuss how such a pathway might allow the virus to assemble so robustly.