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Journal of Virology, January 2000, p. 91-98, Vol. 74, No. 1
Department of Virology, Lerner Research
Institute, Cleveland Clinic Foundation, Cleveland, Ohio
44195,1 and Laboratoire de Genetique
des Virus, CNRS, 91198 Gif sur Yvette cedex, France2
Received 10 June 1999/Accepted 28 September 1999
The phosphoprotein (P) gene of rabies virus (CVS strain) was cloned
and expressed in bacteria. The purified protein was used as the
substrate for phosphorylation by the protein kinase(s) present in cell
extract prepared from rat brain. Two distinct types of protein kinases,
staurosporin sensitive and heparin sensitive, were found to
phosphorylate the P protein in vitro by the cell extract.
Interestingly, the heparin-sensitive kinase was not the ubiquitous
casein kinase II present in a variety of cell types. Further
purification of the cell fractions revealed that the protein kinase C
(PKC) isomers constitute the staurosporin-sensitive kinases
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Copyright © 2000, American Society for Microbiology. All rights reserved.
The Phosphoprotein of Rabies Virus Is
Phosphorylated by a Unique Cellular Protein Kinase and Specific
Isomers of Protein Kinase C
,
,
, and
, with the PKC
isomer being the most effective in
phosphorylating the P protein. A unique heparin-sensitive kinase was
characterized as a 71-kDa protein with biochemical properties not
demonstrated by any known protein kinases stored in the protein data
bank. This protein kinase, designated RVPK (rabies virus protein
kinase), phosphorylates P protein (36 kDa) and alters its mobility in
gel to migrate at 40 kDa. In contrast, the PKC isoforms do not change
the mobility of unphosphorylated P protein. RVPK appears to be packaged
in the purified virions, to display biochemical characteristics similar
to those of the cell-purified RVPK, and to similarly alter the mobility
of endogenous P protein upon phosphorylation. By site-directed
mutagenesis, the sites of phosphorylation of RVPK were mapped at
S63 and S64, whereas PKC isomers phosphorylated
at S162, S210, and S271.
Involvement of a unique protein kinase in phosphorylating rabies virus
P protein indicates its important role in the structure and function of the protein and consequently in the life cycle of the virus.
*
Corresponding author. Mailing address: Department of
Virology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Ave., NC20, Cleveland, OH 44195. Phone: (216) 444-0625. Fax:
(216) 444-0512. E-mail: banerja{at}ccf.org.
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