Studies on the role of the 2'-5'-oligoadenylate synthetase-RNase L pathway in beta interferon-mediated inhibition of encephalomyocarditis virus replication

Interferons inhibit the replication of vesicular stomatitis virus (VSV), but not of encephalomyocarditis virus (EMCV), in mouse JLSV-11 cells. We report the isolation of clonal derivatives from this cell line in which the replication of both viruses is impaired by interferons. These clones were selected from the parental line by virtue of their rescue by interferon treatment from the cytopathic effects of EMCV infection. In one such clone, RK8, the replication of VSV and EMCV and the production of resident murine leukemia virus were inhibited by interferon. On the other hand, in clone RK6, which was isolated without any selection, the replication of VSV, but not of EMCV, was impaired by interferons. The levels of 2'-5'-oligoadenylate synthetase mRNA and enzyme activity were similarly elevated upon interferon treatment in the two clones. However, the level of RNase L, as determined by binding and cross-linking of a radiolabeled 2'-5'-oligoadenylate derivative, was much lower in RK6 cells than in RK8 cells. In accord with this observation, the introduction of 2'-5'-oligoadenylates into cells inhibited protein synthesis much less strongly in RK6 cells than in RK8 cells. These results are consistent with the notion that the 2'-5'-oligoadenylate-dependent RNase L may be a mediator of the inhibition of EMCV replication by interferons.

Characterization of beta-lactamase from Mycobacterium butyricum ATCC 19979

beta-lactamase has been purified to a homogeneous state from Mycobacterium butyricum ATCC 19979. The molecular weight (Mr = 29,000) and the isoelectric point (4,0) of the enzyme have been determined. The enzyme showed both penicillinase and cephalosporinase activity, but had relatively more of the former. With respect to substrate-profile the enzyme resembled the plasmid specified TEM-type beta-lactamases commonly encountered in Gram-negative bacteria. The enzyme was insensitive to p-chloromercuribenzoate, sodium chloride, or iodine inhibition.