Mechanism of the antibiotic action of alpha-dehydrobiotin

alpha-Dehydrobiotin, a naturally occurring biotin analogue, exhibits antibiotic properties [Hanka, L. J., Reineke, L. M., & Martin, D. G.(1969) J. Bacteriol. 100, 42--46]. It is shown in this paper that in addition to its activity as corepressor of the transcription of the biotin locus [Guha, A., Saturen, Y., & Szybalski, W. (1971) J. Mol. Biol. 56, 53--62] alpha-dehydrobiotin acts at the enzyme level. The synthesis of specifically tritiated alpha-dehydrobiotin has been achieved. By use of this labeled compound and a biotin-department strain of Escherichia coli, it has been demonstrated that alpha-dehydrobiotin can be linked covalently to proteins without further transformation. The fixation of biotin to apocarboxylases is inhibited irreversibly after preincubation with alpha-dehydrobiotin. This strongly supports the hypothesis that alpha-dehydrobiotin can be specifically linked to apocarboxylases in place of biotin and leads to carboxylases that are inactive. Thus, the antibiotic properties of alpha-dehydrobiotin would be partly due to the fact that it compete with biotin for the fixation on the apocarboxylases, producing irreversibly inactive enzymes.