Fractionation of the whole cell extract was done according to [23, 40] . The total extract was centrifuged at 21,0006 g at 4uC for 10 min to separate the ''soluble'' (supernatant) and ''membrane'' (pellet) fraction. The pellet was re-suspended and washed with buffer A (30 mM HEPES-KOH pH 7.4, 150 mM potassium acetate, and 5 mM magnesium acetate) followed by centrifugation at 21,0006 g at 4uC for 10 min and re-suspension of the pellet in buffer A. In vitro TBSV replication in the fractions was performed as described [23, 40] .