HOW DOES A VIRUS BUD

How does a virus bud from the plasma membrane of its host? Here we inv estigate several possible rate-limiting processes, including thermal f luctuations of the plasma membrane, hydrodynamic interactions, and dif fusion of the glycoprotein spikes. We find that for bending moduli gre ater than 3 x 10(-13) ergs, membrane thermal fluctuations are insuffic ient to wrap the viral capsid, and the mechanical force driving the bu dding process must arise from some other process. If budding is limite d by the rate at which glycoprotein spikes can diff use to the budding site, we compute that the budding time is 10-20 min, in accord with t he experimentally determined upper limit of 20 min. In light of this, we suggest some alternative mechanisms for budding and provide a ratio nale for the observation that budding frequently occurs in regions of high membrane curvature.