The
biological effect of
B3-tunicamycin, the only known homologue of
tunicamycin which contains a
saturated fatty-acid side chain, was examined using chick embryo fibroblasts, a mouse fibroblastic line (3T3) and a virally transformed mouse fibroblastic line (SV40-3T3). This homologue inhibited the transfer of
N-acetylglucosamine 1-phosphate from
UDP-
N-acetylglucosamine to
dolichyl phosphate, catalyzed by microsomes from chick liver or from cultured mouse fibroblasts.
B3-tunicamycin also inhibited the incorporation of
mannose into
glycoproteins synthesized by chick or mouse fibroblasts. Incorporation of the
amino acids proline and
tyrosine was inhibited by
B3-tunicamycin to a lesser extent than the incorporation of
mannose. The
mannose incorporation into
glycoproteins synthesized by virally transformed cells was inhibited by
B3-tunicamycin to a higher degree than what was achieved in the nontransformed lines or in the chick primary fibroblasts. When the activity of
B3-tunicamycin as an inhibitor of protein glycosylation was compared to other homologues of
tunicamycin, it was found to be the most active. This homologue caused complete (more than 95%) inhibition of protein glycosylation at a concentration of 50 ng/ml in chick and in mouse fibroblasts and at a concentration of 10 ng/ml in transformed mouse fibroblasts. When the cytotoxic activities of
tunicamycin homologues were examined on nontransformed and virally transformed 3T3 cells, it was found that
B3-tunicamycin displayed the highest selective cytotoxicity toward the transformed cells. When transformed fibroblasts (10(5) cells/plate) were treated with
B3-tunicamycin (100 ng/ml) for 48 h, complete cell death was observed. The viability and the proliferative activity of the nontransformed fibroblast were normal even when treated with concentrations up to 500 ng/ml of
B3-tunicamycin. This suggests that
B3-tunicamycin may be a suitable candidate for studies of
tumor growth in animals.