Partial N‐terminal amino acid sequences of polypeptides p14 and p12 of encephalomyocarditis virus are identical and correspond to the N‐terminus of the viral polyprotein

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Abstract
Our previous data suggested that translation in an EMC virus RNA‐programmed cell‐free system from Krebs‐2 cells is initiated predominantly at a single site and that the earliest amino acid sequences synthesized correspond to non‐structural ‘leader’ polypeptides p14 and p12 [(1982) FEBS Lett. 141, 153–156]. Here, polypeptides p14 and p12 were labelled in vitro by tritiated amino acids, isolated and subjected to automated Edman degradation. Both polypeptides (after the loss of the N‐terminal methionine) were shown to contain alanine in position 1 and glutamic acid in positions 5 and 7. These and other data demonstrate that p14 and p12 share a common N‐terminal sequence. This sequence coincides precisely with the N‐terminus of EMC virus polyprotein sequence deduced from the primary structure of the viral genome [(1984) Nucleic Acids Res., in press]. Thus, the single initiation site operating in our translation system corresponds to the start of the polyprotein molecule.