FIG. 1.

Functional domains of MHV-A59 gene 1 and plasmids encoding ORF1a polypeptides. (A) The two ORFs of gene 1, ORF1a and ORF1b, and their predicted functional domains: PLP-1 and PLP-2, X, picornavirus 3C-like proteinase (3CLpro), and hydrophobic (HD1 and HD2). NTPase, nucleoside triphosphatase. (B) Diagrams of plasmids used for transcription and translation of ORF1a polypeptides, along with relevant functional domains and restriction sites. The catalytic residues of PLP-1, Cys1121 and His1272, and the proposed catalytic residues of PLP-2, Cys1716 and His1873, are indicated. The T7 bacteriophage RNA polymerase promoter is designated T7. The cleavages sites for p28 (Gly247/Val248) and p65 (Ala823/Gly833) and the region of ORF1a polypeptide used to raise antiserum UP102 (11) are also indicated. (C) Plasmids used for expression of the PLP domains in E. coli. T7 and ptac are procaryotic promoters for RNA synthesis, and malE encodes MBP.