Erythromycin and spiramycin resistance mutations of yeast mitochondria: nature of the rib2 locus in the large ribosomal RNA gene

Evidence for functional interaction between domains II and V of 23S ribosomal RNA from an erythromycin-resistant mutant

A mutation affording low levels of erythromycin resistance has been obtained by in vitro hydroxylamine mutagenesis of a cloned ribosomal RNA operon from Escherichia coli. The site of the mutational event responsible for antibiotic resistance was localized to the gene region encoding domain II of 23S rRNA by replacement of restriction fragments in the wild-type plasmid by corresponding fragments from the mutant plasmid. DNA sequencing showed that positions 1219-1230 of the 23S rRNA gene are deleted in the mutant. Since all previously characterized rRNA mutations conferring resistance to erythromycin show changes exclusively in domain V, our present findings provide direct evidence for functional interaction between domains II and V of 23S rRNA.

Streptomycin-resistance of Euglena gracilis chloroplasts: identification of a point mutation in the 16S rRNA gene in an invariant position

We sequenced the chloroplast 16S rRNA gene of two Euglena gracilis mutants which contain streptomycin-resistant chloroplasts (Smr 139.12/4 and Smr 139.20/2). These mutants are known to contain a single intact rrn operon per circular chloroplast genome. Nucleotide sequence comparison between a 16S rRNA gene of wild type Euglena gracilis, strain Z, with streptomycin-sensitive chloroplasts, and the 16S rRNA gene of both Smr-strains reveals a single base change (C to T) at position 876. This position is equivalent to the invariant position 912 of the E. coli 16S rRNA gene. The analogous position is also conserved in all chloroplast small subunit RNA genes from lower and higher plants sequenced so far. Light dependent protein synthesis with purified chloroplasts from streptomycin-resistant cells is not inhibited by streptomycin. Based on the results reported here we postulate linkage between the observed point mutation on the 16S rRNA gene and streptomycin-resistance of chloroplast 70S ribosomes.

Primary and secondary structure of 26S ribosomal RNA of Oenothera mitochondria

The primary structure of 26S ribosomal RNA from mitochondria of the dicotyledoneous plant Oenothera berteriana is inferred from the sequence of a cloned rDNA restriction fragment. A tentative secondary structure model valid for Oenothera and for the major part of maize mitochondrial 26S rRNA has been constructed in analogy to the refined german model for E. coli L-rRNA (Maly and Brimacombe 1983). The derived structure generally matches the eubacterial model providing further support to the E. coli consensus structure. Some structural features however show eukaryotic characteristics. Possible interactions between L-rRNA, 5S rRNA and initiator-tRNA are discussed.