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At least 1,099 records · Page 61Linked to original sources
PubMed1992

Structural features of a water-soluble arabinoxylan from the endosperm of wheat.

A cold-water-soluble wheat-endosperm arabinoxylan consisting of a backbone of (1----4)-linked beta-D-xylopyranosyl residues that are variously unsubstituted, and 3- or 2,3-substituted with single alpha-L-arabinofuranosyl groups, was subjected to 1H-n.m.r. spectroscopy. The results of 2D homonuclear Hartmann-Hahn and 1D 1H-n.m.r. spectroscopy allowed the identification of 3- and 2,3-substituted xylose residues, each with adjacent unsubstituted xylose residues, and also substituted xylose residues with a substituted xylose residue as a neighbour. The 1H-n.m.r. data were correlated with 13C-n.m.r. data by means of a 13C-1H 2D proton-detected heteronuclear multiple-quantum correlation experiment, which showed that only different types of branching (i.e., 3- and 2,3-) can be identified by the 13C-n.m.r. data.

Carbohydrate Sequence↗
PubMed1994

Structural features of water-soluble novel polysaccharide components from the leaves of Tridax procumbens Linn.

Two water-soluble polysaccharide fractions, WSTP-IA and WSTP-IB were purified from the leaves of Tridax procumbens Linn. with graded ethanol precipitation followed by mild delignification and size-exclusion chromatography. WSTP-IA contained L-Araf and D-Galp in approximately 1:3 molar proportions, and WSTP-IB contained only D-Galp as the major sugar component. The results of methylation linkage analysis, and 1H and 13C NMR studies on the native and modified polysaccharides, indicated that WSTP-IA is an L-arabino-D-galactan with a beta-(1-->6)-D-galactan main chain in which at least one in every two D-Galp residues carries single residues of either L-Araf (alpha-/beta-) or beta-D-Galp end-group as substituents at O-3. WSTP-IB is a linear beta-(1-->6)-D-galactan. This is the first report of polysaccharides containing a beta-(1-->6)-D-galactan main chain isolated from plant sources.

Arabinose↗
PubMed1990

An analysis of pseudocontact shifts and their relationship to structural features of the redox states of cytochrome b5.

The assignment of proton resonances in both redox states of a heme protein is necessary for the evaluation of pseudocontact shift data. Many new assignments are presented here for cytochrome b5, particularly in the paramagnetic oxidised state, thereby allowing both the calculation of electronic g-tensor values with the magnetic axis orientation and a comparison of observed and calculated pseudocontact shifts utilising a computational procedure. The possible redox linked conformational changes are found to be minimal in contrast with cytochrome c although the procedure additionally highlights aspects of the mobility of certain residues in cytochrome b5. In this respect the residue Gly-42 appears mobile both by this method and by the observation from NMR spectra of a major and minor conformation in this region.

Amino Acid Sequence↗
PubMed1988

Micropia: a retrotransposon of Drosophila combining structural features of DNA viruses, retroviruses and non-viral transposable elements.

The retrotransposon micropia was first described from Y-chromosomal fertility genes of Drosophila hydei. Screening a Drosophila melanogaster genomic library yielded several clones representing micropia elements in D. melanogaster. The DNA sequences of two elements from D. hydei (micropia-DhMiF2 and micropia-DhMiF8) and two elements from D. melanogaster (micropia-Dm2 and micropia-Dm11) permitted a detailed analysis of the spatial organization of micropia constituents. Micropia represents the typical gene organization represented by "core"-protein domains followed by a protease, reverse transcriptase, RNase and integrase domain. New features of the micropia family compared with other retrotransposons are: (1) a region of similarity to class I major histocompatibility complex antigens of mammals; (2) only one main open reading frame of about 4000 bases length; (3) a non-protein-coding region of about 500 base-pairs length between the 3' end of the open reading frame and the 5' start of the 3' long terminal repeat. This region includes 32 base-pair tandem repeats; (4) within the long terminal repeats, 82 base-pair tandem repeats with four potential ecdysteroid receptor binding sites. Because micropia combines many evolutionary features of different viruses, non-viral transposable elements, chromosomal genes and repetitive sequence organizations, this retrotransposon may be seen as a "minigenome" reflecting evolutionary principles of the construction of genomic components.

Amino Acid Sequence↗
PubMed1988

Functional regions and structural features of the gB glycoprotein of herpes simplex virus type 1. An analysis of linker insertion mutants.

Glycoprotein B (gB) of Herpes simplex virus type 1 (HSV-1) plays an essential role in viral entry. A set of more than 100 HpaI (GTTAAC) linker insertion mutations and their derivatives were isolated in plasmids specifying the gB coding and flanking sequences. Mutations including addition, deletion and nonsense mutations at 34 independent sites were identified by DNA sequence analysis of 48 plasmids. A map was constructed for the ability of addition mutants to complement a gB-null virus. The expression of gB activity for some plasmids was temperature-dependent. Many complementation-negative plasmids inhibited the complementation activity of a plasmid specifying wild-type gB, suggesting an interaction between active and inactive molecules to form oligomers. The interaction was localized to 328 of the total of 904 amino acids comprising gB. Partial Endo H digestion of nonsense polypeptides revealed that five of the six potential N-linked oligosaccharide sites are glycosylated; the most C-terminal site appears not to be glycosylated. A number of mutations, including some on the cytoplasmic side, were identified that blocked processing, transport and secretion. Addition mutations that blocked processing of membrane polypeptides also blocked processing and secretion when combined into a nonsense mutant that by itself was processed and secreted. The previously predicted membrane spanning domain and the membrane orientation of the N-terminal portion of gB were confirmed.

Amino Acid Sequence↗
PubMed1983

Structural features of very fast sedimenting DNA formed by gene 49 defective T4.

Very fast sedimenting DNA (VFS DNA) of T4 phage, which is formed by infection with a mutant in gene 49, was examined by electron microscopy after mild treatment with DNase I. It showed Y-shaped, branched strands in addition to linear strands. Each branch contained a single-stranded interruption about 60 nucleotides long at its proximal end. The average number of branches per T4 DNA unit was close to the average number of sites susceptible to gene 49 nuclease. Both numbers were consistently changed by the addition of a secondary mutation in a gene involving recombination.

Centrifugation, Density Gradient↗
PubMed1986

Nucleotide sequence of the Bunyamwera virus M RNA segment: conservation of structural features in the Bunyavirus glycoprotein gene product.

The complete nucleotide sequence of the Bunyamwera virus M RNA segment was determined from four overlapping cDNA clones and by primer extension. The RNA segment is 4458 bases in length, and encodes a single gene product in the viral complementary RNA. The predicted protein is 1433 amino acids long (mol wt 162,065), contains four potential glycosylation sites, and is relatively cysteine rich. It is presumed that the three proteins G1, G2, and NSM which have been mapped to the M RNA segment are synthesized as a precursor polyprotein which is subsequently proteolytically cleaved. A putative hydrophobic signal sequence at the amino terminus and a hydrophobic anchor sequence at the carboxy terminus of the predicted protein have been identified, in addition to internal regions of hydrophobicity of unknown function. The nucleotide and amino acid sequences of the Bunyamwera virus M segment have been compared with those of the snowshoe hare virus M segment (Y. Eshita and D. H. L. Bishop, Virology 137, 227-240, 1984). Common features include the overall architecture of the RNAs, single cysteine-rich primary gene products, and conservation of hydrophobic domains in the gene products. When aligned the amino acid sequences are 43% homologous, and 66 of 70 cysteine residues can be matched. The evolutionary significance of these findings is discussed.

Amino Acid Sequence↗