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J. Virol., 02 1995, 809-813, Vol 69, No. 2
SA Hughes, PJ Bonilla and SR Weiss
Mouse hepatitis virus strain A59 encodes a papain-like cysteine proteinase
(PLP-1) that, during translation of ORF1a, cleaves p28 from the amino
terminus of the growing polypeptide chain. In order to determine the amino
acid sequences surrounding the p28 cleavage site, the first 4.6 kb of
murine hepatitis virus strain A59 ORF1a was expressed in a cell-free
transcription-translation system. Amino- terminal radiosequencing of the
resulting downstream cleavage product demonstrated that cleavage occurs
between Gly-247 and Val-248. Site- directed mutagenesis of amino acids
surrounding the p28 cleavage site revealed that substitutions of Arg-246
(P2) and Gly-247 (P1) nearly eliminated cleavage of p28. Single-amino-acid
substitutions of other residues between P7 and P2' were generally
permissive for cleavage, although a few changes did greatly reduce
proteolysis. The relationship between the p28 cleavage site and other viral
and cellular papain proteinase cleavage sites is discussed.
Copyright © 1995, American Society for Microbiology
Identification of the murine coronavirus p28 cleavage site
Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia 94104-6076.
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