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Journal of Virology, August 1999, p. 6626-6633, Vol. 73, No. 8
Laboratory of Infectious Diseases, National
Institute of Allergy and Infectious Diseases, National Institutes
of Health, Bethesda, Maryland
Received 23 February 1999/Accepted 4 May 1999
Expression of the region of the feline calicivirus (FCV) ORF1
encoded by nucleotides 3233 to 4054 in an in vitro rabbit reticulocyte system resulted in synthesis of an active proteinase that specifically processes the viral nonstructural polyprotein. Site-directed
mutagenesis of the cysteine (Cys1193) residue in the
putative active site of the proteinase abolished autocatalytic cleavage
as well as cleavage of the viral capsid precursor, suggesting that this
"3C-like" proteinase plays an important role in proteolytic
processing during viral replication. Expression of the region encoding
the C-terminal portion of the FCV ORF1 (amino acids 942 to 1761) in
bacteria allowed direct N-terminal sequence analysis of the
virus-specific polypeptides produced in this system. The results of
these analyses indicate that the proteinase cleaves at amino acid
residues E960-A961,
E1071-S1072,
E1345-T1346, and
E1419-G1420; however, the cleavage efficiency
is varied. The E1071-S1072 cleavage site
defined the N terminus of a 692-amino-acid protein that contains
sequences with similarity to the picornavirus 3C proteinase and 3D
polymerase domains. Immunoprecipitation of radiolabeled proteins from
FCV-infected feline kidney cells with serum raised against the FCV ORF1
C-terminal region showed that this "3CD-like" proteinase-polymerase
precursor protein is apparently stable and accumulates in cells during infection.
0022-538X/99/$04.00+0
Mapping of the Feline Calicivirus Proteinase
Responsible for Autocatalytic Processing of the Nonstructural
Polyprotein and Identification of a Stable Proteinase-Polymerase
Precursor Protein
*
Corresponding author. Mailing address: 9000 Rockville
Pike, Building 7, Room 137, Bethesda, MD 20892. Phone: (301) 496-5811. Fax: (301) 496-8312. E-mail: kgreen{at}niaid.nih.gov.
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