<div><p>(A) The positions of mutations responsible for the <i>ts</i> phenotype of selected MHV-A59 mutants are illustrated in relation to the non-structural proteins (nsp1–16) produced by proteolytic processing of the ORF1a/ORF1b polyprotein, pp1ab. Nucleotide changes are numbered according to the sequence of the infectious cDNA clone of MHV-A59.</p><p>(B) The amino acid substitutions responsible for the mutant and revertant phenotypes are listed together with the mutated protein and the cistron to which each mutant has been assigned. The amino acids are numbered from the amino-terminus to the carboxyl-terminus of each of the non-structural proteins.</p></div
