Oxazolidinones are a promising new class of synthetic antibiotics active against multidrug‐resistant Gram‐positive bacteria. To elucidate their mode of action, the effect of DuP 721 on individual steps of protein translation was studied. The drug does not interfere with translation initiation at the stage of mRNA binding or formation of 30S pre‐initiation complexes. However, it inhibits the puromycin‐mediated release of [ 35 S]formyl‐methionine from 70S initiation complexes in a dose‐dependent manner. Inhibition involves binding of the oxazolidinone to the large ribosomal subunit and is twice as high with 50S subunits from Gram‐positive as with those from Gram‐negative bacteria.
Abstract Dedicated to Prof. Aloysius Wild on the occasion of his 65th birthday Lepidium sativum, Cruciferin, Ribulosebisphosphate Carboxylase, Inhibition of Transcription Cress (Lepidium sativum) seeds were germinated in darkness. Seedlings were investigated for soluble proteins by SDS-PAGE. Two proteins were identified by microsequencing: the small subunit of ribulosebisphosphate carboxylase (SSU) and the alpha subunit of the storage protein cruciferin. Net synthesis of small and large subunits of ribulosebisphosphate carboxylase (SSU and LSU) was investigated by Western blot. Net synthesis of both subunits was inhibited by coumarin. To the contrary, net synthesis of cruciferin was increased by coumarin. With specific cDNA probes, we determined steady state levels of the corresponding mRNAs (rbcS mRNA for SSU, rbcL mRNA for LSU). Both mRNAs can be detected in dry seeds; their amount increases during germination in the dark. Incubation with coumarin inhibits this increase. Inhibition of development by coumarin on the level of transcription is discussed.
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