Dem IPB wird erneut ein beispielhaftes Handeln im Sinne einer chancengleichheitsorientierten Personal- und Organisationspolitik bescheinigt. Das Institut erhält zum 6. Mal in Folge das TOTAL E-QUALITY…
Die Plant Science Student Conference (PSSC) wird seit 20 Jahren im jährlichen Wechsel von Studierenden der beiden Leibniz-Institute IPK und IPB organisiert. Im Interview erläutern Christina Wäsch…
Mikkat, S.; Milkowski, C.; Hagemann, M.;The gene sll 0273 of the cyanobacterium Synechocystis sp. strain PCC6803 encodes a protein essential for growth at low Na+/K+ ratiosPlant Cell Environ.23549-559(2000)DOI: 10.1046/j.1365-3040.2000.00565.x
A mutant of Synechocystis sp. strain PCC6803 was obtained by random cartridge mutagenesis, which could not grow at low sodium concentrations. Genetic analyses revealed that partial deletion of the sll 0273 gene, encoding a putative Na+ /H+ exchanger, was responsible for this defect. Physiological characterization indicated that the sll 0273 mutant exhibited an increased sensitivity towards K+ , even at low concentrations, which was compensated for by enhanced concentrations of Na+ . This enhanced Na+ demand could also be met by Li+ . Furthermore, addition of monensin, an ionophore mediating electroneutral Na+ /H+ exchange, supported growth of the mutant at unfavourable Na+ /K+ ratios. Measurement of internal Na+ and K+ contents of wild‐type and mutant cells revealed a decreased Na+ /K+ ratio in mutant cells pre‐incubated at a low external Na+ /K+ ratio, while it remained at the level of the wild type after pre‐incubation at a high external Na+ /K+ ratio. We conclude that the Sll0273 protein is required for Na+ influx, especially at low external Na+ concentrations or low Na+ /K+ ratios. This system may be part of a sodium cycle and may permit re‐entry of Na+ into the cells, if nutrient/Na+ symporters are not functional or operating.
Publikation
Hinneburg, A.; Keim, D. A.; Brandt, W.;Clustering 3D-structures of small amino acid chains for detecting dependences from their sequential context in proteinsProc. IEEE International Symposium on Bio-Informatics and Biomedical Engineering43-49(2000)DOI: 10.1109/BIBE.2000.889588
In the past, a good number of rotamer libraries have been published, which allow a deeper understanding of the conformational behavior of amino acid residues in proteins. Since the number of available high-resolution X-ray protein structures has grown significantly over the last years, a more comprehensive analysis of the conformational behavior is possible today. In this paper, we present a method to compile a new class of rotamer libraries for detecting interesting relationships between residue conformations and their sequential context in proteins. The method is based on a new algorithm for clustering residue conformations. To demonstrate the effectiveness of our method, we apply our algorithm to a library consisting of all 8000 tripeptide fragments formed by the 20 native amino acids. The analysis shows some very interesting new results, namely that some specific tripeptide fragments show some unexpected conformation of residues instead of the highly preferred conformation. In the neighborhood of two asparagine residues, for example, threonine avoids the conformation which is most likely to occur otherwise. The new insights obtained by the analysis are important in understanding the formation and prediction of secondary structure elements and will consequently be crucial for improving the state-of-the-art of protein folding.