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J. Virol., Oct 1996, 6909-6921, Vol 70, No. 10
S Cudmore, R Blasco, R Vincentelli, M Esteban, B Sodeik, G Griffiths and J Krijnse Locker
We describe herein the characterization of p39, the product of the A4L gene
of vaccinia virus. By immunolabelling of thawed cryosections from infected
HeLa cells, we show that this protein is initially located in the central
region, or viroplasm, of the viral factories, as well as in the immature
virions, with very small amounts of labelling observed on the surrounding
membranes. The localization of p39 changes dramatically during the
transition of the immature virion to the intracellular mature virus (IMV),
coincident with the appearance of the core structure in the center of the
IMV, with p39 located between this core and the surrounding membranes.
Complementary biochemical data, such as partitioning into the Triton X-114
detergent phase and stripping of the viral membranes with Nonidet P-40 and
dithiothreitol, suggest that p39 is associated with the innermost of the
two membranes surrounding the core. Sodium carbonate treatment also
indicates that p39 is associated with membranes, even at the early stages
of viral assembly. However, following in vitro translation of p39 in the
presence of microsomal membranes, we failed to detect any association of
the independently expressed protein with membranes. We also failed to
detect any posttranslational acylation of p39 with myristate or palmitate,
suggesting that p39 does not achieve its membrane association through lipid
anchors. Therefore, p39 is most likely membrane associated through an
interaction with an integral membrane protein(s) present in the innermost
of the two membranes surrounding the IMV. These data, together with our
recent data showing that p39 colocalizes with the spike-like protrusions on
the IMV core (N. Roos, M. Cyrklaff, S. Cudmore, R. Blasco, J.
Krijnse-Locker, and G. Griffiths, EMBO J. 15:2343-2355, 1996), suggest that
p39 may form part of this spike and that it possibly functions as a
matrix-like linker protein between the core and the innermost of the two
membranes surrounding the IMV.
Copyright © 1996, American Society for Microbiology
A vaccinia virus core protein, p39, is membrane associated
Cell Biology Program, European Molecular Biology Laboratory, Heidelberg, Germany.
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