Biomedical subjects
Publications and source records attributed to J L Strominger.
Spore cortex of conditional cortexless mutants of Bacillus sphaericus 9602 was not detectable by electron microscopy unless the medium was supplemented with meso-alpha,epsilon-diaminopimelic acid during sporulation. Other spore structures appeared normal. Spore shape was quite irregular in the absence of meso-alpha,epsilon-diaminopimelic acid.
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HL-A antigens having specificities HL-A2, HL-A7, HL-A12 have been solubilized by papain treatment of membrane preparations from the cultured human lymphoblastoid cell line RPMI 4265 and purified about 80-fold by chromatography on carboxymethylcellulose, Sephadex G-150, and diethylaminoethylcellulose columns. Separation of HL-A2 from a mixture of HL-A7 and HL-A12 was achieved on the final DEAE-cellulose column. The yield was about 1 mg of protein of each antigen preparation per 100 g of packed, frozen cells. On sodium dodecyl sulfate gel electrophoresis both preparations showed two polypeptide bands. The smaller subunit of 12,000 daltons is common to all HL-A preparations and has been shown to be identical with beta2-microglobulin. The larger subunit is a glycopeptide and in the HL-A7, 12 preparation was resolved into a duplex of 34,000 and 37,000 daltons. The HL-A2 preparation showed a single band at 34,000 daltons. On isoelectric focusing under nondenaturing conditions, the preparation showed multiple bands, all of which contained both subunits and retained antigenic activity. On isoelectric focusing in the presence of 6 M urea a single band for beta2-microglobulin and multiple bands for the larger subunit were seen. This charge heterogeneity of the larger subunit has been shown to be due to variable amounts of sialic acid. When HL-A antigen preparations were subjected to Sephadex G-100 chromatography in the presence of 3 M KCl, no separation of the two subunits was observed.
Three preparations of purified papain-solublized HL-A antigens have been radiolabeled by reductive methylation using formaldehyde and potassium boro[3H]hydride, and their reaction with specific HL-A antisera has been investigated. Greater than 99 percent of the radioactivity in the [3H]HL-A2 preparation could be complexed with several HL-A2 antisera, but not with specificity controls. The other two preparations, which contained mixtures of HL-A antigenic specificities (HL-A7,12 an HL-A3,W25;12,27), showed 63 per cent and 70 per cent complex formation with mixtures of the appropriate HL-A antisera. The N-terminal amino acid of both subunits has been determined for the three HL-A antigen preparations. In all cases the only detectable N-terminal amino acids were isoleucine for the small subunits, beta-2-microblogulin, and glycine for the larger subunit.
A DNA-synthesizing system in vitro, using nuclei prepared by treatment of human lymphocytes with the detergent Brij 58, was developed. Nuclei from cultured lymphocytes synthesized DNA for as long as 5 hr, and required ATP, deoxynucleoside triphosphates, magnesium, and a calcium chelator. In nuclei from a partially synchronized line of cultured lymphocytes carrying several hundred copies of the Epstein-Barr viral genome, synthesis in vitro was predominately viral in early S phase and cellular in late S phase. These and other data suggested that the DNA synthesis observed in vitro was predominately replicative.
The amount of HL-A antigens present on the peripheral blood lymphocytes of a single human donor was increased about 11-fold after stimulation with phytohemagglutinin and 36-fold after transformation with Epstein-Barr virus. This increase applied to all four HL-A specificities of these cells. The response to phytohemagglutinin was dependent on dose and was first observed at 12 hr of incubation. Measurements of the amount of surface membranes by geometry, by radioiodinatable surface proteins, and by 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) assay all indicated that the enhanced representation of HL-A antigens after stimulation by phytohemagglutinin or transformation by Epstein-Barr virus must be due to an increase in the density of these antigens on the cell surface.
D-Alanine carboxypeptidase from Bacillus stearothermophilus is a membrane-bound enzyme which is inhibited by covalent interaction with penicillin G. The penicilloyl enzyme spontaneously reactivates and simultaneously releases a penicillin G degradation product; 0.2 mumol of the latter was isolated after incubation of 4.2 mumol of [8-14C]penicillin G with 10 g of membrane protein. It was identified as phenylacetylglycine by chromatographic techniques, infrared spectroscopy, and mass spectrometry. A mechanism for the degradation is proposed in which the remaining part of penicillin G would be released as 5,5-dimethyl-delta2-thiazoline-4-carboxylic acid. The implications of this finding are discussed.
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A simple and quick procedure was used to analyse the carbohydrate composition of surface glycoproteins from chicken lymphocytes. The procedure included papain digestion of the cells, a two-step purification of the supernatant material and a sugar analysis by gaschromatography. The method made it possible to analyse samples of about 10(9) lymphocytes. The surface glycoproteins from different chicken lymphocyte preparations were found to differ significantly in their sugar composition. Lymphocytes from thymus, bursa, spleen or blood were characterized by typical relative amounts of glucose, galactosamine, fucose and sialic acid. The values for mannose, glucosamine and galactose, however, were approximately 1:1:1 for all four lymphocyte preparations. Bursectomy or thymectomy in combination with whole body irradiation altered the carbohydrate composition significantly. The results suggest the possibility that the carbohydrate composition can be used as a marker for different lymphocyte populations. The results are also discussed in respect to the hypothesis that carbohydrate determinants on the cell surface determine the migration of lymphocytes.
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