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Biomedical subjects

O Pongs

Publications and source records attributed to O Pongs.

At least 181 records · Page 10Linked to original sources
PubMed1973

Identification of chloramphenicol-binding protein in Escherichia coli ribosomes by affinity labeling.

Monoiodoamphenicol, a synthetic analogue of chloramphenicol, has been shown by competition experiments with chloramphenicol and lincomycin to bind at the same site of 70S ribosomes as chloramphenicol. At - 2 degrees it forms a 1:1 complex with 70S ribosomes having a value of K (7.5 x 10(4) M(-1)) that is one order of magnitude lower than that of chloramphenicol. At 37 degrees , monoiodoamphenicol irreversibly inhibits the protein-synthesizing activity of E. coli ribosomes. It is shown that the analogue reacted preferentially with protein L16 of E. coli 70S ribosomes, and we therefore conclude that protein L16 belongs to the chloramphenicol-binding site of E. coli ribosomes. Since the chemically reactive group of monoiodoamphenicol resembles iodoacetamide, the reaction of E. coli 70S ribosomes with monoiodoamphenicol was compared to that with iodoacetamide. Iodoacetamide did not react with protein L16, but it predominantly reacted with proteins S18 of the 30S subunit. Furthermore, monoiodoamphenicol was reacted with E. coli ribosomal subunits. Isolated 50S subunits bound monoiodoamphenicol by about one order of magnitude less than 70S ribosomes. Again, protein L16 reacted with the affinity label. Monoiodoamphenicol reacted with protein S18 in isolated 30S subunits; it also bound to 70S ribosomes of Bacillus stearothermophilus, however, it did not bind irreversibly to these 70S ribosomes.

Acetamides↗
PubMedDate not supplied

Structural basis of potassium channel diversity in the nervous system.

A variety of voltage-sensitive potassium channels has been described which differ in their electrophysiological and pharmacological properties. Potassium channels which mediate outward K+ currents in response to changes in membrane polarisation differ most notably in their voltage sensitivity and their opening and closing kinetics, as well as their recovery times from inactivation. Also, some of these potassium channels are sensitive to toxins like dendrotoxin and mast cell degranulating peptide; others are not. We have cloned and sequenced a variety of cDNAs encoding potassium channel subunits present in invertebrate as well as vertebrate central nervous systems. Injection into Xenopus oocytes of RNA synthesized in vitro using the various cDNAs as a template results in the expression of functional potassium channels. Some of these channels exhibit properties similar to those of the non-inactivating delayed rectifier channel found in many excitable cells, yet differ in their sensitivities towards potassium channel blocking agents. The properties of other channels expressed from cRNA injected into Xenopus oocytes resemble those of transient A-type channels which inactivate rapidly after opening upon membrane depolarisation. A comparison of the derived primary sequences of the different potassium channels allows a direct correlation of channel protein structures with electrophysiological and pharmacological properties, respectively.

Animals↗