Search PubMed⌕ Search

Biomedical subjects

A Rich

Publications and source records attributed to A Rich.

At least 343 records · Page 19Linked to original sources
PubMed1976

Pre-proparathyroid hormone. Evidence for an early biosynthetic precursor of proparathyroid hormone.

Pre-proparathyroid hormone, discovered previously by the translation of messenger RNA from parathyroid glands in heterologous cell-free systems, is a polypeptide of 115 amino acids consisting of 25 amino acids added to the NH2 terminus of proparathyroid hormone (90 amino acids), the immediate biosynthetic precursor of parathyroid hormone (84 amino acids). We now have detected pre-proparathyroid hormone formation within intact parathyroid cells, thus providing direct evidence that it is a biosynthetic precursor of proparathyroid hormone. A radiolabeled protein synthesized by slices of bovine parathyroid glands during 1 to 10 min of incubation with [35S] methionine was identified that co-migrated on both urea-acetate and urea-SDS acrylamide gels with 3H-labeled pre-proparathyroid hormone prepared by mRNA translation in a cell-free system derived from wheat germ. The amount of radiolabeled protein reached a maximum 3 min after exposure of the tissue to[35S] methionine and decreased during a 3-min chase incubation with unlabeled methionine. It bound to antisera to both proparathyroid hormone and parathyroid hormone and contained 35S-labeled tryptic peptides that migrated identically with peptides of pre-proparathyroid hormone prepared from the wheat germ system. Radiolabeled proparathyroid hormone was identified in the tissue after 1 min of incubation with [35S] methionine. These findings indicate that pre-proparathyroid hormone is an early biosynthetic precursor of proparathyroid hormone in parathyroid tissue and that this precursor is converted to proparathyroid hormone within 1 min after completion of its synthesis on the rough endoplasmic reticulum.

Animals↗
PubMed1976

Pre-proparathyroid hormone: analysis of radioactive tryptic peptides and amino acid sequence.

The amino acid sequence of bovine pre-proparathyroid hormone has been partially determined by analysis of the polypeptide labeled selectively with radioactive amino acids. Analysis of tryptic peptides containing methionine or lysine indicated that parathyroid hormone, proparathyroid hormone, and pre-proparathyroid hormone had several common peptides. Two lysine-containing peptides present in proparathyroid hormone but not in parathyroid hormone were also present in pre-proparathyroid hormone. In addition, pre-proparathyroid hormone contained several additional lysine- and methionine-containing peptides not present in parathyroid hormone or proparathyroid hormone. Analysis by repetitive Edman degradation of the polypeptide labeled with lysine, methionine, and other amino acids indicated that pre-proparathyroid hormone contained 25 additional amino acids at the amino terminus of proparathyroid hormone; the identities of 17 of the 25 amino acids have been established. An unusual feature found was the presence of methionyl-methionyl at the amino terminus and the presence of 5 methionines within the first 14 amino acids.

Amino Acid Sequence↗
PubMed1976

Pre-proparathyroid hormone: fidelity of the translation of parathyroid messenger RNA by extracts of wheat germ.

Pre-proparathyroid hormone is the major protein synthesized in wheat-germ extracts in response to addition of an 8-15S fraction of parathyroid RNA. The accuracy of the translation of the mRNA from parathyroid tissue was examined by analysis of the carboxyl-terminal tryptic peptide and the amino-terminal amino acid of the protein, by analysis of the size distribution of the mRNA, and by translation of the mRNA in a second cell-free extract. When 8-15S RNA was fractionated on a sucrose gradient containing formamide, RNA that supported the synthesis of pre-proparathyroid hormone was present in a single symmetrical peak, suggesting that it was homogeneous. Analyses by paper chromatography and electrophoresis of the proline-containing tryptic peptides of pre-proparathyroid hormone indicate that they are identical with the corresponding proline-containing peptides of parathyroid hormone. Because the COOH-terminal tryptic peptide of parathyroid hormone contains proline, the data indicate that the COOH termini of pre-proparathyroid hormone and parathyroid hormone are identical. Methionine from initiator [35S]Met-tRNAfMet was rapidly incorporated into pre-proparathyroid hormone by the wheat-germ extract, and a single-step Edman degradation selectively removed almost all of the initiator [35S]methionine present in pre-proparathyroid hormone. Translation of the 8-15S RNA in a cell-free extract from Krebs-II ascites cells resulted in a protein that comigrated with pre-proparathyroid hormone on sodium dodecyl sulfate-acrylamide gel electrophoresis. These data support the conclusion that the wheat-germ system accurately translates the mRNA for parathyroid hormone, and they strengthen the contention that pre-proparathyroid hormone is the initial biosynthetic product.

Animals↗
PubMed1976

Tissue-specific forms of actin in the developing chick.

Actin has been identified in nonmuscle and muscle tissues as a highly conserved homogeneous protein. We have identified and characterized actin from embryonic and adult chick brain and muscle, and have compared these actins by SDS and urea/SDS gradient polyacrylamide gel electrophoresis. In the presence of SDS alone, embryonic or adult brain and muscle actin co-migrate as homogeneous polypeptides. Electrophoresis of both actins in the presence of urea and SDS, however, reveals that brain and muscle actins migrate with distinctly different mobilities. Actin from embryonic thigh muscle at different stages of development migrates as two separate components. In early muscle development, only the "brain" type actin is present. As muscle development progresses the "muscle" type actin becomes relatively more abundant, so that by day 20 of embryonic development, "muscle" actin becomes predominant. These results may be interpreted as due to differences in the primary structure of actin.

Actins↗
PubMed1976

Sequence-specific recognition of double helical nucleic acids by proteins.

The base pairs in double helical nucleic acids have been compared to see how they can be recognized by proteins. We conclude that a single hydrogen bond is inadequate for uniquely identifying any particular base pair, as this leads to numerous degeneracies. However, using two hydrogen bonds, fidelity of base pair recognition may be achieved. We propose specific amino-acid side chain interactions involving two hydrogen bonds as a component of the recognition system for base pairs. In the major groove we suggest that asparagine or glutamine binds to adenine of the base pair or arginine binds to guanine. In the minor groove, we suggest an interaction between asparagine or glutamine with guanine of the base pair. We also discuss the role that ions and other amino-acid side chains may play in recognition interactions.

Hydrogen Bonding↗
PubMed1976

Chick cytoplasmic actin and muscle actin have different structural genes.

Actins isolated from embryonic chick brain and muscle differ in mobility when subjected to electrophoresis in gels containing urea and sodium dodecyl sulfate. Experiments were carried out to determine whether these actins are products of different structural genes and differ in primary amino acid sequence, or whether they are products of the same structural gene but are different because of post-translational modification. Messenger RNA from brain and muscle tissue was used to direct cell-free protein synthesis in wheat germ extracts. The synthesized actins were identified by conversion from globular to fibrous actin and by two-dimensional chromatographic analysis of tryptic peptides. The differences in electrophoretic mobility of brain compared to muscle actin were maintained in the cell-free protein synthetic products. Therefore, these mobility differences were not due to post-translational modification. It was concluded that brain and muscle actin are coded by different messenger RNAs and therefore arise from different structural genes. In addition, messenger RNA from 13- and 16-day embryonic thigh muscle directed the synthesis of both brain- and muscle-type actins, suggesting that muscle cell differentiation involves the regulation of at least two different actin genes.

Actins↗
PubMed1976

Direct biochemical mapping of eukaryotic viral DNA by means of a linked transcription-translation cell-free system.

A method is described for mapping regions of eukaryotic viral DNA coding for specific proteins, utilizing a linked transcription-translation cell-free system primed with DNA fragments generated by restriction endonucleases. Three simian virus 40 (SV40) DNA fragments derived from that region of the DNA expressed late in lytic infection were purified. They were: Hpa I-A (0.76-0.175 map units), Bgl I-EcoRI-B (0.672-0), and Hpa II-EcoRI-B (0.735-0). (Fragments are named from the cleaving restriction endonuclease and electrophoretic mobility. End positions on the conventional map are in clockwise order.) These fragments efficiently stimulated the incorporation of [3H]UTP and [35S]methionine into trichloroacetic-acid-insoluble material in the linkec system. The location of the region of DNA coding for the viral structural proteins VPI, VP2 and VP3 was determined from the spectrum of polypeptide synthesis directed by the individual intact fragments and their specific endonucleolytic digests. The polypeptides synthesized in the cell-free system were characterized on urea-sodium dodecyl sulfate polyacrylamide gradient gels and by two-dimensional tryptic peptide analysis. ..

Cell-Free System↗
PubMed1975

Raman spectra and structure of yeast phenylalanine transfer RNA in the crystalline state and in solution.

Laser Raman spectra of yeast phenylalanine transfer RNA have been obtained in solution and in orthorhombic and hexagonal crystals. So far as one can tell from the spectra, which are identical in the two crystal forms, the molecular structure of the tRNA is not altered by differences in molecular packing in these two unit cells. In addition, the spectra of the two crystal forms show the same characteristic Raman frequencies and intensities as those of the tRNA in aqueous solution. Thus the structure of the tRNA molecule appears to be the same in the crystals and in aqueous solution. From the spectroscopic changes that result when Mg2+ ions are removed from the native tRNA, it is concluded that the removal of Mg2+ produces a partial disordering of the ribophosphate backbone of the molecule and a lowering of its melting temperature. The melting is shown to be a complex process in that the vibrations specific for adenine indicate a slightly lower melting temperature and those specific for guanine a slightly higher melting temperature than that of the ribophosphate backbone.

Binding Sites↗