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Biomedical subjects

G R Reeck

Publications and source records attributed to G R Reeck.

At least 55 records · Page 3Linked to original sources
PubMed1978

Analysis of the effectiveness of sodium chloride in dissociating non-histone chromatin proteins of cultured hepatoma cells.

We examined the ability of NaCl (at 0.15 to 3 M) to release non-histone proteins from chromatin of cultured rat hepatoma cells. The percentage of the non-histones released increased with increasing NaCl concentrations up to 0.75 M; 1 and 3 M NaCl were not significantly more effective. A maximum of 50% of the non-histone protein was recovered free of DNA. The release of non-histones from sheared and unsheared chromatin was similar. The electrophoretic patterns of the non-histone proteins released by NaCl resembled that of the non-histones released by sodium dodecyl sulfate, which indicates that many of the detectable components were at least partially released by NaCl. Some non-histones (especially low molecular weight polypeptides) were fully released by NaCl and other proteins were relatively resistant to NaCl release. Higher recoveries of NaCl-dissociated non-histones were obtained with sucrose gradient centrifugation than with centrifugation in the absence of sucrose.

Animals↗
PubMed1978

The evolution of histones.

The amino acid sequences of bovine histones H2A, H2B, H3, and H4 and the first 107 residues of rabbit thymus histone H1 were examined using newly developed procedures designed to detect and evaluate weak similarities (de Haën et al., 1976). Using the McLachlan scoring system, regions of statistically significant similarity were found between several pairs of the four smallest histones. The probability that this set of similarities could result simply from chance was estimated to be less than 10(-5). No similarity was found between the H1 sequence and the other histones. The results are interpreted to indicate that at least the C-terminal portions of the core histones evolved from a common ancestral protein.

Amino Acid Sequence↗
PubMed1977

Isolation and characterization of trypsin inhibitor from opaque-2 corn seeds.

Trypsin inhibitor was isolated from seeds of opaque-2 corn by affinity chromatography on a trypsin/Sepharose column. The two major forms of inhibitor eluted from the affinity column were separated by DEAE-cellulose chromatography in the presence of urea. One form of inhibitor is a single-chain protein that has a molecular weight of approximately 12,500; the second inhibitor has two polypeptide chains and appears to have been produced from the single-chain inhibitor by exposure to trypsin in the affinity chromatography step. The relationship of the inhibitor isolated from opaque-2 corn to an inhibitor previously isolated from an unspecified strain of maize by Hochstrasser et al. (Hochstrasser, K., Muss, M., and Werle, E. (1967) Z. Physiol. Chem. 348, 1337-1340) is discussed.

Chromatography, Affinity↗
PubMed1977

Association products and conformations of salt-dissociated and acid-extracted histones. A two-phase procedure for isolating salt-dissociated histones.

We present an extremely rapid and efficient method for the separation of salt-dissociated histones from DNA in which the macromolecular components of chicken erythrocyte chromatin are partitioned in a two-phase system of the water-soluble, nonionic polymers, poly(ethylene glycol) and dextran. We have compared the association products and conformations of salt-dissociated histones purified with the two-phase procedure and histones that had been extracted with 0.4 M H2SO4. In the gel chromatography system of D. R. vander Westhuyzen and C. von Holt (1971), FEBS Lett. 14, 333-337] the association products of salt-dissociated and acid-extracted histones are indistinguishable. Furthermore, the circular dichroism spectra of histones prepared with the two methods are identical within experimental error. These results indicate that histones extracted, with sulfuric acid can adopt conformations at least very similar to those of salt-dissociated preperties of total erythrocyte histones are the same in 2 M NaCl as those of these histones bound to DNA in chromatin in 1 mM Tris-Cl (pH 7.5). This result and the studies of Weintraub et al. [Weintraub, H., Palter, K., and Van Lente, F. (1975), Cell 6, 68-110] on the patterns of tryptic digest products of histones strongly suggest that in 2 M NaCl the histones exist in conformations very similar to their conformations when bound to DNA. The concept of native histone conformations is discussed in light of our results.

Animals↗
PubMed1972

Resolution of a spectrum of nucleoprotein species in sonicated chromatin.

Sonicated rabbit-liver chromatin is fractionated by ion-exchange chromatography on ECTHAM-cellulose, a weakly cationic adsorbent. The chromatographic procedure provides a series of fractions having a spectrum of thermal denaturation profiles. The earliest-eluting fractions melt cooperatively at a significantly higher temperature than bulk chromatin, and totally lack any of the components of chromatin that melt at low temperatures. In contrast, the latest-eluting fractions are significantly enriched in their content of DNA sequences that melt at low temperatures. Although the protein to DNA mass ratio of all fractions is equal to that of unfractionated chromatin, polyacrylamide gel electrophoresis demonstrates that the relative amounts of individual proteins vary across the chromatographic peak. The most pronounced changes observed are the enrichment of a particular high molecular weight nonhistone protein in the later fractions, and a significant diminution of lysine-rich histone in the last fractions. The results, in conjunction with the demonstration by McConaughy, B. L. & McCarthy, B. J. (Biochemistry 11, 998-1003, 1972) that RNA transcribed in vivo in immature chick erythrocytes hybridizes to the DNA of only the portions of chromatin from these cells that melt at low temperatures, suggest that this fractionation may separate transcribable DNA sequences in chromatin from the repressed segments of a eukaryotic genome.

Animals↗
PubMed1971

New forms of bovine carboxypeptidase B and their homologous relationships to carboxypeptidase A.

Two new forms of carboxypeptidase B have been isolated from spontaneously activated bovine pancreatic juice. The fully active enzymes contain an internal split at residues 92-93 and 95-96, respectively. Sequenator analysis of the amino terminal segments of the two chains of the enzyme has extended the sequence information by 51 amino acid residues. Comparison of 125 residues strengthens the hypothesis that carboxypeptidases A and B are homologous both in amino acid sequence and in three-dimensional conformation and implicates Asp-255 as the anionic site of substrate binding of the B enzyme.

Amino Acid Sequence↗