Self-assembly of a viral molecular machine from purified protein and RNA constituents

We present the assembly of the polymerase complex (procapsid) of a dsRNA vi rus from purified recombinant proteins. This molecular machine packages and replicates viral ssRNA genomic precursors in vitro. After addition of an e xternal protein shell, these in vitro self-assembled Viral core particles c an penetrate the host plasma membrane and initiate a productive infection. Thus, a Viral procapsid has been assembled and rendered infectious using pu rified components. Using this system, we have studied the mechanism of asse mbly of the common dsRNA virus shell and the incorporation of a symmetry mi smatch within an icosahedral capsid. Our work demonstrates that this molecu lar machine, self-assembled under defined conditions in vitro, can function in its natural environment, the cell cytoplasm.