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Fig. 3. Octameric ring-like structure adopted by Ebola virus VP40 after
its association with specific, single-stranded RNA. ( A ) Ribbon drawing of
the ring structure. ( B ) Close-up stereo view of VP40-RNA interactions.
Courtesy of Gomis-Ruth et al ., 2003.
domain of VP40 may thus prevent VP40 aggregation in the cyto-
plasm, while VP40 association with the plasma membrane may trig-
ger VP40 oligomerization for the formation of virus particles.
Recent data indicate that VP40 octamerization is critical for Ebola
virus replication. 14 Dimeric structures in the VP40 octamer form a
pocket at their interface, which binds a short, single-stranded RNA
molecule with the sequence: 5
. This RNA-dimer complex
helps to stabilize the structure 15 (Fig. 3). Two amino acids, Phe125
and Arg134, are critical for RNA binding. Their replacement impedes
octamerization, but it does not affect VLP formation or virion mor-
phology. 14 A recombinant virus containing an Arg134-to-Ala replace-
ment in VP40 could not be recovered, 14 confirming that VP40
octamer formation is likely critical for the Ebola viral lifecycle.
-U-G-A-3
Assembly of VP40 and GP
Several groups have used recombinant DNA technology to demonstrate
that Ebola virus VP40 expressed in mammalian cells is released into
the culture medium in membrane-bound form. 6,9,13,16 The virosome-
like particles containing VP40 were verified by flotation analysis and a
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