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M Vauhkonen

Publications and source records attributed to M Vauhkonen.

43 records · Page 3Linked to original sources
PubMed1985

High-mannose structure of apolipoprotein-B from low-density lipoproteins of human plasma.

Human plasma low-density lipoproteins were purified by flotation followed by gel filtration. The protein moiety of the lipoproteins, apolipoprotein-B, which was detected by polyacrylamide gel electrophoresis as the only protein component, contained 4.4% (by weight) carbohydrate. Glycopeptides liberated from apolipoprotein-B by pronase were fractionated by affinity chromatography on concanavalin-A--Sepharose. The results indicated that high-mannose glycopeptides interacting strongly with the lectin comprise about 37% of the total monosaccharides of apolipoprotein-B. Thus, as compared to the total serum glycoproteins having about 5% of their monosaccharides in high-mannose glycopeptides, low-density lipoproteins are relatively enriched in these structures amounting up to about 10% of the total high-mannose oligosaccharides in serum. The rest of the carbohydrates in low-density lipoproteins are suggested to be mainly biantennary acidic oligosaccharides interacting weakly with concanavalin A. The oligomannosidic chains from native low-density lipoproteins and isolated glycopeptides were released by digestion with endo-beta-N-acetylglucosaminidase H. Thin-layer chromatography of the released oligosaccharides indicated that apolipoprotein-B contains five different oligomannosidic structures varying in the number of the mannose residues from Man5GlcNAc to Man9GlcNAc. Separation of the per-O-benzoylated high-mannose oligosaccharides by high-pressure liquid chromatography revealed the same polymeric structures in a molar ratio (from Man5 to Man9) of 10:2:3:2:3. Apolipoprotein-B in low-density lipoproteins was calculated to contain five high-mannose chains in total. The different high-mannose oligosaccharides liberated by endo-beta-N-acetylglucosaminidase H were isolated with high-pressure liquid chromatography after reduction with NaBH4, and subjected to methylation analysis with gas-liquid chromatography--mass spectrometry. The data of these studies and the results of exoglycosidase treatment suggest the following structure for the main high-mannose oligosaccharide: (formula: see text) The higher polymeric structures are composed of chains in which the Man5GlcNAc structure is continued by one to four Man(alpha 1-2) residues.

Apolipoproteins B↗
PubMed1985

Solubilization of proteins in dimethyl sulfoxide by permethylation: application to structural studies of apolipoprotein B.

The delipidated protein moiety, apolipoprotein B, of human low-density lipoproteins was permethylated in potassium butoxide/dimethyl sulfoxide with methyl iodide. The derivatized protein was soluble in dimethyl sulfoxide and, in the presence of sodium dodecyl sulfate, in an aqueous buffer. Analysis of the methylated apolipoprotein B by polyacrylamide gradient gel electrophoresis in the presence of sodium dodecyl sulfate revealed five discrete bands of lower molecular mass than that of the parent 265-kDa protein, which disappeared upon permethylation. The electrophoretic behavior of the methylated apolipoprotein B was distinctly different from that of the other methylated proteins studied, including transferrin, bovine serum albumin, aldolase, beta-lactoglobulin, and apolipoprotein A-I, all of which had a higher apparent molecular weight after permethylation as compared to the corresponding native polypeptide. Calculated on the basis of methylated standard proteins the five polypeptides of apolipoprotein B have apparent molecular masses of 9.0, 16.6, 25.6, 35.7, and 46.7 kDa. The results suggest that the protein moiety of human low-density lipoprotein consists of subunits. In general, the results indicate that the permethylation method can be used to solubilize hydrophobic proteins in organic solvents for structural studies.

Apolipoproteins B↗
PubMed1980

Serum and tissue distribution of benzol[a]pyrene from intravenously injected chylomicrons in rat in vivo.

Rats were injected intravenously with chylomicrons (CM) containing benzo[a]pyrene (B[a]P), a carcinogenic aromatic hydrocarbon. The disappearance of B[a]P paralleled the removal of CM, both having a rapid initial decay and a secondary slow decay. After 5 min, at the end of the rapid phase, blood contained 19% of the total injected B[a]P, with 6% in blood cells and 13% in serum. At 60 min, serum contained 5% and blood cells 6% of the total B[a]P. During the slow phase, further distribution of B[a]P within serum albumin and various lipoproteins occurred, most of the label being in low density and very low density lipoproteins. Highest tissue specific activities of [3H]B[a]P were in the lung, liver and kidney tissues. These results suggest that in the rat, distribution of ingested polycyclic aromatic hydrocarbons in vivo tends to be primarily determined by the catabolism of chylomicrons.

Animals↗
PubMed1979

Binding of benzo(a)pyrene into lung and thymocyte nuclear fractions.

Binding of (3H)benzo(a)pyrene into lung and thymocyte nuclear fractions is studied in short term cultures. DNA, RNA and protein in the subnuclear fractions is separated and tightly bound radioactivity is measured. Among the fractions, proteins of the matrix sediment fraction display the highest specific radioactivity. DNA has a low specific radioactivity as compared to that of RNA and protein in all fractions. In thymocyte matrix extract and chromatin fractions the specific radioactivity of RNA exceeds that of protein. Lung nonhistones display a 30 times higher specific radioactivity as compared to histones. The corresponding ratio of the thymocyte fractions is about 10.

Animals↗
PubMed1977

Distribution of estrogen receptors in hen oviduct chromatin fractions in the course of DNAase II digestion.

Hen oviduct chromatin was digested with DNAase II and two fractions were isolated: MgCl2-insoluble chromatin and MgCl2-soluble chromatin. The former contained 14 and 50% of the total DNA after a digestion time of 3 and 30 min, respectively. The fraction was characterized in sucrose gradients by a peak sedimenting at 11S. In the course of DNAase digestion this fraction lost most of its estrogen receptors as assayed by [3H]estradiol exchange reaction. The specific radioactivity of chromatin was particularly low in the 11S region. The MgCl2-soluble chromatin contained at most 5.1% of the total DNA. In sucrose gradients the fraction displayed peaks at 4S and 14S. After a 30 min DNAase digestion the specific radioactivity of chromatin in this fraction exceeded that of the MgCl2-insoluble fraction 7.7 fold. Material sedimenting at 14 S and at larger S values was enriched in estrogen receptors. The results suggest that estrogen receptors are unevenly distributed on hen oviduct chromain.

Animals↗
PubMed1977

Polylysine titration of rat liver chromatin fractions after DNase II digestion.

The concentration of free phosphate groups is measured in rat liver chromatin after DNase II digestion using polylysine titration. The unsheared chromatin completely precipitates at lysine/DNA phosphate ratios of 0.5 to 0.6. Digestion of the chromatin reduces the lysine/DNA phosphate ratio of complete precipitation by about 0.2 units suggesting the removal of free phosphate groups. The two chromatin fractions: MgC12 insoluble (template-inactive) and Mg12 soluble (template-active) chromatins precipitate at about the same lysine/DNA phosphate ratio. Some 15% of the MgC12 soluble chromatin remains in solution at any polylysine concentration. The removal of histone H 1 FROM THE MgC12 insoluble chromatin increases the lysine/DNA phosphate ratio by about 0.2 units suggesting that 20% of the DNA phosphate groups in nucleosomes are masked by histone H 1.

Animals↗