Biomedical subjects
Publications and source records attributed to S Kühn.
Three mutations caused by the integration of IS4 in galT in both possible orientations were shown by DNA sequence analysis to be integrated between a duplication of eleven base pairs of gene galT. IS4 has been cloned from its single position on the E. coli K12 chromosome. Here, 12 base pairs are duplicated adjacent to IS4. This sequence is unrelated to the duplicated sequence in galT.
Four insertions of IS1 in the leader sequence of the gal operon of E. coli have been analysed. Two of them occur at the same position, but in opposite orientations. The other two are inserted one nucleotide to one side and four nucleotides to the other side, respectively. In each case, nine base pairs of the leader sequence of the gal operon are duplicated directly, and are found flanking the termini of IS1 at its junction with the gal operon. These repeated sequences differ from each other as expected from the different insertion sites.
Acid phosphatase isozymes were investigated in cancerous prostatic tissue (4 cases) and benign prostatic hyperplasia (6 cases). Electron-microscopic histochemical examination of cancer tissue revealed irregular acid beta-glycerophosphatase staining in various cell organelles, including the plasma membrane, which was not seen in non-malignant tissue. Cancerous tissue homogenates also contained isozymic acid phosphatase species with high electrophoretic mobility, which was not detectable in benign tissue unless treated with detergent. Fractionation by differential centrifugation confirmed that much of the acid phosphatase activity in cancer tissue was extra-lysosomal. The detection of these isozyme properties may provide an opportunity, by means of tissue investigations, to define tumour stages earlier than on the basis of increased levels of serum acid phosphatase activity indicative of stage IV (D) prostatic cancer.
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Non-epithelial intermediate filament (IF) subunit proteins show a high and specific affinity for core histones at physiological ionic strength. When IF proteins are titrated with a mixture of core histones and linker histone H1, in general the latter is totally excluded from complexation and in the adducts formed the moderately-arginine-rich histones H2A and H2B are progressively replaced by the very-arginine-rich histones H3 and H4. At histone saturation, 2 molecules of nonneuronal IF protein bind 1 histone H1 molecule or 8 core histone molecules, whereas due to its glutamic acid-rich, C-terminal extensions one dimer of the 68 kD neurofilament protein associates with 3 molecules of histone H1 or 24 molecules of core histones. The salt stability of the insoluble association products is dependent on the amount and arginine content of the constituent histone species. Removal of the non-alpha-helical N- and C-terminal polypeptides from IF proteins by partial chymotryptic digestion does not affect their histone-binding characteristics. Since core histones are only partially inactivated by limited tryptic digestion, they also appear to react through their alpha-helix-rich central domains; the limit peptide derived from histone H1 is completely inactive at physiological ionic strength. Affinity chromatography of rod domains of IF proteins on core histone-Sepharose 4B and of histones and their limit peptides on vimentin-Sepharose 4B has shown that the interactions involving fractions of histones H3 and H4 are extremely resistant to salt and can be dissociated only with arginine or salt under denaturing conditions. In general, the experimental results revealed close parallels between the association of histones with IF proteins and their interaction with DNA.