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Biomedical subjects

K Willecke

Publications and source records attributed to K Willecke.

At least 163 records · Page 9Linked to original sources
PubMed1977

Human mitochondrial thymidine kinase is coded for by a gene on chromosome 16 of the nucleus.

The expression of human mitochondrial thymidine kinase (mt TK) was investigated by polyacrylamide electrophoresis in 19 independent human-mouse somatic cell hybrids which allowed all human chromosomes to be analyzed. In 8 hybrid clones the presence of this enzymatic activity could be demonstrated. Human mt TK segregated concordantly with human adenine phosphoribosyltransferase (APRT) and human chromosome 16. Discordant segregation with all other human chromosomes was demonstrated by karyotype and isozyme analyses. These results suggest that human mt TK is coded for by a gene on chromosome 16 of the nucleus. Thus human mt TK is genetically different from human cytosol thymidine kinase which is coded for by a gene on chromosome 17. The appearance of one heteropolymer band after electrophoretic separation of human and murine mt TK supports the notion that both enzymes have dimeric structures.

Chromosome Mapping↗
PubMed1976

Cotransfer of two linked human genes into cultured mouse cells.

Two linked human genes which code for the expression of cytosol thymidine kinase (ATP:thymidine 5'-phosphotransferase, EC 2.7.1.75) and galactokinase (ATP:D-galactose 1-phosphotransferase, EC 2.7.1.6) have been cotransferred via purified metaphase chromosomes from the human lymphoblastoid cell line WI-L2a, into mouse L-cells [B82 and LM(TK-)]. Both genes have previously been shown to be closely linked on the human chromosome E17, band q21-22. Coexpression of both human enzyme markers was detected in two out of eight gene transfer clones, whilst the remaining six clones contained only human cytosol thymidine kinase, as shown by electrophoretic techniques. A further 23 human enzyme markers corresponding to 15 different human chromosomes were found to be absent in these gene transfer clones. No human chromosome or chromosomal fragment could be detected by karyotype analyses. Some of the gene transfer clones rapidly lost the transferred donor material when grown in nonselective medium, whereas others expressed a stable phenotype under these conditions. Prolonged maintenance in selective medium favors the survival of gene transfer cells expressing a stable phenotype. Possibly these cells harbor the donor genes integrated into a recipient chromosome.

Cells, Cultured↗
PubMed1975

Competent Bacillus subtilis cultures synthesize a denatured DNA binding activity.

A protein activity has been detected in soluble extracts of competent cultures of bacillus subtilis which protects denatured DNA from nuclease solubilization. Both binding activity and competence development occur simultaneously but not coordinately, since the peak of binding activity appears 3 hr after the peak of competence. The binding activivity is not detected in physiologically noncompetent cultures, in an isogenic noncompetent cultures, in an isogenic noncompetent mutant grown through the competence regimen, or in early sporulating cells. The activity is included on Sephadex G-100 gel filtration columns but elutes in a broad nonhomogeneous peak. This binding activity may play a role in uptake of DNA and/or integration of exogenous DNA into the genome of competent B. subtilis cells.

Bacillus subtilis↗
PubMed1975

Transfer of the human gene for hypoxanthine-guanine phosphoribosyltransferase via isolated human metaphase chromosomes into mouse L-cells.

We have transferred the human gene for hypoxanthine-guanine phosphoribosyltransferase (HPRT, EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferease) via isolated metaphase chromosomes from human HeLa S3 cells into murine A9 cells which lack functional murine HPRT activity, using the technique of McBride and Ozer (Proc, Nat. Acad. Sci. USA 70, 1258-1262, 1973). Three transformed clones were isolated which contained human HPRT activity as determined by electrophoretic and immunochemical assays. Twenty human isozymes other than HPRT whose genes have been assigned to 14 human chromosomes were found to be absent in our transformed clones. Moreover, the human isozymes of hlucose-6-phosphate dehydrogenase (EC 1.1.1.49; D-glucose 6-phosphate:NADP 1-oxidoreductase) and phosphoglycerate kinase (EC 2.7.2.3;ATP:3-phospho-D-glycerate 1-phosphotransferase), whose genes have been linked with the HPRT gene to the long are of the human X chromosome, were also absent. On the basis of the known linkage relationships of the three markers, we thereby suggest that the transferred piece of human genetic material is smaller than 20% of the human X chromosome or less than 1% of the human genome. This estimate assumes a normal syntenic relationship for the long arm of the X chromosome in HeLa S3 cells. In agreement with this conclusion, no human chromosomes could be detected in our transformed clones. When grown under nonselective conditions about 3% of the gene transfer cells lost the human HPRT marker per cell generation. Transformants that had lost human HPRT activity were subjected to hypoxanthine-aminopterin-thymidine selection. The frequency of revertants to the HPRT(+) phenotype was less than 1 x 10(-6), and two revertants that were obtained possessed the mouse electrophoretic phenotype. These results argue against a stable integration of the human donor genetic material into the mouse recipient genome.

Animals↗
PubMed1975

Inhibition of de novo fatty acid synthesis by the antibiotic cerulenin in Bacillus subtilis: effects on citrate-Mg2+ transport and synthesis of macromolecules.

Inhibition of de novo fatty acid biosynthesis by the antibiotic cerulenin in Bacillus subtilis stopped de novo synthesis of neutral lipids and phospholipids. The bacteria ceased growing but remained completely viable. Addition of 12-methyltetradecanoic acid and palmitic acid to the culture medium of cerulenin-treated cells restored growth of the bacteria, albeit at a reduced rate. Although the de novo synthesis of all lipid components of the membrane was blocked, citrate-Mg(2+) transport activity remained inducible, and induced cells did not lose this transport activity when treated with cerulenin. Shortly after the addition of cerulenin, the rate of ribonucleic acid synthesis dropped rapidly and was followed by a slower decrease in the rate of protein synthesis. The rate of deoxyribonucleic acid synthesis remained almost unaffected. The rapid decrease of ribonucleic acid synthesis in cerulenin-treated cells might be due to the inhibition of de novo fatty acid biosynthesis or it might be due to a secondary effect of cerulenin in B. subtilis cells.

Adenosine Triphosphate↗