Presence of a common structure in the two molecular species of mouse L cell interferon

Tryptic digests of the two molecular species of purified mouse L cell interferon, labeled with [¹²⁵I] and [³H] methionine, were analyzed chromatographically. The 40,000 dalton-species yielded 4 methionine-containing and 6 [¹²⁵I]-labeled fragments, whereas the 24,000 dalton-species gave rise to 4 methionine- and 7 [¹²⁵I]-labeled fragments. Of these, 3 methionine-containing and 3 [¹²⁵I]-labeled fragments were found chromatographically identical between the two species. These results suggest that the two distinct species of interferon contain a common polypeptide structure.