Penicillinase plasmids of Staphylococcus aureus: restriction-deletion maps.
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Genes↗
Biomedical subjects
I Edelman
Publications and source records attributed to I Edelman.
Genetic translocation in Staphylococcus aureus.
A 5.2-kilobase pair transposon, Tn551, has been found in Staphylococcus aureus, a Gram-positive bacterium. Initially detected on plasmid pI258, it undergoes rec-independent transposition to multiple chromosomal and plasmid sites, sometimes causing insertional inactivation. Unlike most other transposons, Tn551 undergoes apparently precise excision as a rule. The initial observation of Tn551 transition involved UV inactivation of the carrier plasmid; this would appear to be a general means of detecting transposable elements.
Chromosome Deletion↗
Translocatable elements in Staphylococcus aureus.
The properties of the first translocatable element in Gram-positive bacteria, a 5.2 kb segment encoding erythromycin resistance in S. aureus, are described. This element translocates from plasmid to multiple chromosomal sites and from chromosome to multiple plasmid sites, sometimes causing insertional inactivation and deletion. The genetic control of translocation and its role in natural plasmid evolution are discussed and preliminary evidence for translocation of penicillin and chloramphenicol resistance is presented. In the latter case, translocation involves in intact plasmid.
Chloramphenicol↗
Solubilization of a stereospecific opiate-macromolecular complex from rat brain.
A [3H]etorphine-macromolecular complex has been solubilized from rat brain synaptosomal fraction by extraction with the nonionic detergent Brij 36T. Stereospecificity of binding to this solubilized complex was demonstrated by the finding that radioactivity in the complex was virtually eliminated when binding had occurred in the presence of excess levorphanol, an active narcotic analgesic, while it was unaffected by its inactive enantiomorph dextrorphan. Bound radioactivity was dissociated by proteolytic enzymes, sulfhydryl reagents, and heat, suggesting the presence of protein. The bound solubilized macromolecular moiety may be the opiate receptor.
Animals↗
Opiate receptors and their interactions with agnoists and antagonists.
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Allosteric Regulation↗
Further properties of stereospecific opiate binding sites in rat brain: on the nature of the sodium effect.
Addition of sodium salts has been reported to enhance stereospecific binding of opiate antagonists while reducing binding of agonists to rat brain homogenate. We have tested, in addition to sodium and potassium, a number of organic cations. Our results support the suggestion that the ability to enhace antagonist binding is not a general characteristic of cations or high ionic strength, but a property of sodium ions. We have shown that the increase in antagonist binding results from an enhancement of binding affinity and not from unmasking of new binding sites. The reduction in etorphine binding in the presence of sodium is due to a decrease in binding affinity. This decrease is largely accounted for by an acceleration in the dissociation rate, while the greater affinity of naltrexone binding appears to be due to an increase in rate of association. Our results are consistent with the hypothesis of a conformational change in opiate binding sites in the presence of sodium, transformed sites exhibiting greater affinity for antagonists and reduced affinity for agonists. Preheating of rat brain P2 fraction at 50 degrees C results in gradual inactivation of stereospecific binding, but an increase in naltrexone binding is consistently observed after heating at 50 degrees C for 2 to 3 minutes, even at optimal concentrations of sodium.
Analgesics, Opioid↗