Biomedical subjects

R Cedergren

Publications and source records attributed to R Cedergren.

40 records · Page 3Linked to original sources

PubMed1985

Nucleotide sequences of two serine tRNAs with a GGA anticodon: the structure-function relationships in the serine family of E. coli tRNAs.

We have determined the nucleotide sequence of the major species of E. coli tRNASer and of a minor species having the same GGA anticodon. These two tRNAs should recognize the UCC and UCU codons, the most widely used codons for serine in the highly expressed genes of E. coli. The two sequences differ in only one position of the D-loop. Neither tRNA has a modified adenosine in the position 3'-adjacent to the anticodon. This can be rationalized on the basis of a structural constraint in the anticodon stem and may be related to optimization of the codon-anticodon interaction. Comparison of all E.coli serine tRNAs (and that encoded by bacteriophage T4) reveals characteristic (possibly functional) features. Evolutionary analysis suggests an eubacterial origin of the T4 tRNASer gene and the existence of a recent common ancestor for the tRNASerGGA and tRNASerGUC genes.

Anticodon↗

PubMed1985

Cooperativity in low-affinity Mg2+ binding to tRNA.

The Pb2+-catalyzed cleavage of tRNAPhe has been used to probe the effect of Na+ and Mg2+ binding to tRNA. Na+ is a noncompetitive inhibitor of the Pb2+-catalyzed cleavage. Millimolar Mg2+ is also a noncompetitive inhibitor. Analysis of the Mg2+ data show that at least two sites are involved in binding and that there is an interaction between the sites (cooperativity). Low-affinity Mg2+ binding is thus different from "weak" and "strong" Mg2+ binding to tRNA characterized previously. We postulate that the alterations induced by low-affinity Mg2+ binding in tRNA mimic to some extent those brought about in RNA by the interaction with a protein factor and that at appropriate [Mg2+] the whole structure of tRNA is able to respond in a concerted way to a signal from the environment such as aminoacylation or codon binding.

Binding Sites↗

PubMed1985

Probing fungal mitochondrial evolution with tRNA.

Sequence data are now available for almost the entire complement of mitochondrial rRNAs from five fungi: Schizosaccharomyces pombe, Saccharomyces cerevisiae, Toropulis glabrata, Aspergillus nidulans and Neurospora crassa. Analysis of these data show that the five mitochondria can be related to a common ancestor. The unusually high similarity between some S. pombe mt tRNAs may be due to a process similar to gene conversion. Using the number of differences between tRNA pairs as a measure of the evolutionary rate the yeast-S. pombe branch has paradoxically a high nuclear rate and a low mt rate of evolution as compared with other branches in the phylogenetic tree. Finally the position of mt tRNA genes in S. pombe is abnormally distinct from gene orders in other mitochondria. All of the above factors must be taken into account when describing the relationship between these mitochondria.

Base Sequence↗

PubMedDate not supplied

The evolutionary relationships among known life forms.

Sequences of small subunit (SSU) and large subunit (LSU) ribosomal RNA genes from archaebacteria, eubacteria, and the nucleus, chloroplasts, and mitochondria of eukaryotes have been compared in order to identify the most conservative positions. Aligned sets of these positions for both SSU and LSU rRNA have been used to generate tree diagrams relating the source organisms/organelles. Branching patterns were evaluated using the statistical bootstrapping technique. The resulting SSU and LSU trees are remarkably congruent and show a high degree of similarity with those based on alternative data sets and/or generated by different techniques. In addition to providing insights into the evolution of prokaryotic and eukaryotic (nuclear) lineages, the analysis reported here provides, for the first time, an extensive phylogeny of the mitochondrial lineage.

Base Sequence↗