In vitro ubiquitination of VP40. VP40-WT and
VP40-dPY were transcribed and translated in vitro (lanes
1 and 4, respectively). In vitro translated proteins
were incubated with recombinant E1 and E2 (UBC8) proteins, ATP,
ubiquitin, and either WT Rsp5 (lanes 2 and 5) or the C-A mutant form of
Rsp5, as indicated (lanes 3 and 6). The position of the VP40 doublet
(lanes 1–6) and multiubiquitinated forms of VP40 [VP40-ub(n); lane
2] are indicated. A positive control (52-kDa yeast protein encoded by
the YHL002w gene; G.W. and J.H., unpublished data) for ubiquitination
by Rsp5 is shown (lanes 7 and 8). The arrowhead depicts the location of
the nonubiquitinated form of the 52-kDa protein. The presence or
absence of WT Rsp5 or mut. Rsp5 is indicated by a + or −.