Structural characterization of the N-linked oligosaccharides in bile salt-stimulated lipase originated from human breast milk.
The detailed structures of N- glycans derived from bile salt-stimulated lipase (BSSL) found in human milk were determined by combining exoglycosidase digestion with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The N- glycan structures were conclusively determined in terms of complexity and degree of fucosylation. Ion-exchange chromatography with pulsed amperometric detection, together with mass-spectral analysis of the esterified N- glycans, indicated the presence of monosialylated structures. The molecular mass profile of esterified N- glycans present in BSSL further permitted the more detailed studies through collision-induced dissociation (CID) and sequential exoglycosidase cleavages. The N- glycan structures were elucidated to be complex/dibranched, fucosylated/complex/dibranched, monosialylated/complex/dibranched, and monosialylated/fucosylated/dibranched entities. (+info)
Alternative splicing of transcripts encoding the alpha- and beta-subunits of mouse glucosidase II in T lymphocytes.
Glucosidase II is a processing enzyme of the endoplasmic reticulum that functions to hydrolyze two glucose residues in immature N -linked oligosaccharides attached to newly synthesized polypeptides. We previously reported the cDNA cloning of the alpha- and beta-subunits of mouse glucosidase II from T cells following copurification of these proteins with the highly glycosylated transmembrane protein-tyrosine phosphatase CD45. Subsequent examination of additional cDNA clones, coupled with partial genomic DNA sequencing, has revealed that both subunits are encoded by gene products that undergo alternative splicing in T lymphocytes. The catalytic alpha-subunit possesses two variably expressed segments, box Alpha1, consisting of 22 amino acids located proximal to the amino-terminus, and box Alpha2, composed of 9 amino acids situated between the amino-terminus and the putative catalytic site in the central region of the molecule. Box Beta1, a variably expressed 7 amino acid segment in the beta-subunit of glucosidase II, is located immediately downstream of an acidic stretch near the carboxyl-terminus. Screening of reverse transcribed RNA by polymerase chain reaction confirms the variable inclusion of each of these segments in transcripts obtained from a panel of T-lymphocyte cell lines. Thus, distinct isoforms of glucosidase II exist that may perform specialized functions. (+info)
A novel human SRB/MED-containing cofactor complex, SMCC, involved in transcription regulation.
A novel human complex that can either repress activator-dependent transcription mediated by PC4, or, at limiting TFIIH, act synergistically with PC4 to enhance activator-dependent transcription has been purified. This complex contains homologs of a subset of yeast mediator/holoenzyme components (including SRB7, SRB10, SRB11, MED6, and RGR1), homologs of other yeast transcriptional regulatory factors (SOH1 and NUT2), and, significantly, some components (TRAP220, TRAP170/hRGR1, and TRAP100) of a human thyroid hormone receptor-associated coactivator complex. The complex shows direct activator interactions but, unlike yeast mediator, can act independently of the RNA polymerase II CTD. These findings demonstrate both positive and negative functional capabilities for the human complex, emphasize novel (CTD-independent) regulatory mechanisms, and link the complex to other human coactivator complexes. (+info)
Structure of cag pathogenicity island in Japanese Helicobacter pylori isolates.
BACKGROUND: cag pathogenicity island (PAI) is reported to be a major virulence factor of Helicobacter pylori. AIM: To characterise cagA and the cag PAI in Japanese H pylori strains. METHODS: H pylori isolates from Japanese patients were evaluated for CagA by immunoblot, for cagA transcription by northern blot, and for cagA and 13 other cag PAI genes by Southern blot. cagA negative strains from Western countries were also studied. Induction of interleukin-8 secretion from gastric epithelial cells was also investigated. RESULTS: All Japanese strains retained cagA. Fifty nine of 63 (94%) strains had all the cag PAI genes. In the remaining four, cag PAI was partially deleted, lacking cagA transcripts and not producing CagA protein. Details of the PAI of these strains were checked; three lacked cagB to cagQ (cagI) and continuously cagS to cag13 (cagII), and the remaining one lacked cagB to cag8. Western cagA negative strains completely lacked cag PAI including cagA. Nucleotide sequence analysis in one strain in which the cag PAI was partially deleted showed that the partial deletion contained 25 kb of cag PAI and the cagA promoter. Interleukin-8 induction was lower with the cag PAI partial deletion strains than with the intact ones. All Japanese cag PAI deleted strains were derived from patients with non-ulcer dyspepsia, whereas 41 of 59 (70%) CagA-producing strains were from patients with peptic ulcers or gastric cancer (p<0.05). CONCLUSIONS: Most Japanese H pylori strains had the intact cag PAI. However, some lacked most of the cag PAI in spite of the presence of cagA. Thus the presence of the cagA gene is not an invariable marker of cag PAI related virulence in Japanese strains. (+info)
Biased JH usage in plasma cell immunoglobulin gene sequences from colonic mucosa in ulcerative colitis but not in Crohn's disease.
BACKGROUND: Ulcerative colitis is an inflammatory disease of the colonic and rectal mucosa. Autoantibodies have been observed in ulcerative colitis which may have a role in the pathogenesis of the disease. Evidence also suggests that there is an hereditary predisposition towards the disease, although no individual genes have been identified. AIMS: This is a pilot study of immunoglobulin heavy chain genes (IgH) in ulcerative colitis to determine whether they have any particular genetic characteristics which may lead to a better understanding of the disease aetiology. SUBJECTS: Colonic or rectal tissue was obtained from five children with ulcerative colitis. Tissue was also obtained from five children with Crohn's disease and five children who did not have inflammatory bowel disease as controls. METHODS: B cells and IgD+ B cells were identified by immunohistochemistry on frozen sections. Areas of lamina propria containing plasma cells, and areas of IgD+ B cells were microdissected. The immunoglobulin genes were PCR amplified, cloned, and sequenced. Sequences were analysed for content of somatic mutations and composition of heavy chain. RESULTS: An increase in the use of JH6 and DXP'1, and a decrease in the use of JH4, gene segments in immunoglobulin genes from lamina propria plasma cells, and from virgin IgD+ B cells, was found in patients with ulcerative colitis. These biases were not present in the control groups. CONCLUSIONS: There is a fundamental difference in the immunoglobulin genes from patients with ulcerative colitis. Whether this is caused by a difference in content of immunoglobulin gene segments in the germline or a difference in the recombination mechanism is not known. (+info)
The origin and evolution of green algal and plant actins.
The Viridiplantae are subdivided into two groups: the Chlorophyta, which includes the Chlorophyceae, Trebouxiophyceae, Ulvophyceae, and Prasinophyceae; and the Streptophyta, which includes the Charophyceae and all land plants. Within the Streptophyta, the actin genes of the angiosperms diverge nearly simultaneously from each other before the separation of monocots and dicots. Previous evolutionary analyses have provided limited insights into the gene duplications that have produced these complex gene families. We address the origin and diversification of land plant actin genes by studying the phylogeny of actins within the green algae, ferns, and fern allies. Partial genomic sequences or cDNAs encoding actin were characterized from Cosmarium botrytis (Zygnematales), Selaginella apoda (Selaginellales), Anemia phyllitidis (Polypodiales), and Psilotum triquetrum (Psilotales). Selaginella contains at least two actin genes. One sequence (Ac2) diverges within a group of fern sequences that also includes the Psilotum Ac1 actin gene and one gymnosperm sequence (Cycas revoluta Cyc3). This clade is positioned outside of the angiosperm actin gene radiation. The second Selaginella sequence (Ac1) is the sister to all remaining land plant actin sequences, although the internal branches in this portion of the tree are very short. Use of complete actin-coding regions in phylogenetic analyses provides support for the separation of angiosperm actins into two classes. N-terminal "signature" sequence analyses support these groupings. One class (VEG) includes actin genes that are often expressed in vegetative structures. The second class (REP) includes actin genes that trace their ancestry within the vegetative actins and contains members that are largely expressed in reproductive structures. Analysis of intron positions within actin genes shows that sequences from both Selaginella and Cosmarium contain the conserved 20-3, 152-1, and 356-3 introns found in many members of the Streptophyta. In addition, the Cosmarium actin gene contains a novel intron at position 76-1. (+info)
Cell-specific peptide binding by human neutrophils.
Analysis of peptide binding to human neutrophils (PMN) using phage display techniques has revealed cell-specific motifs reactive with the PMN surface. Phage libraries displaying either linear 9-mer or cyclic 10-mer and 6-mer peptides were incubated with normal human neutrophils followed by elution of bound phage with low pH (pH 2.2) and non-ionic detergent. Three rounds of selection generated several related peptide sequences that bound with high avidity to PMN. Using the linear 9-mer library, PMN-binding phage expressed peptides with the motif (G/A)PNLTGRW. The binding of phage bearing this motif was highly specific since no binding was observed on lymphocytes, fibroblasts, epithelial, or endothelial cells. Functional assays revealed that phage bearing the sequence FGPNLTGRW induced a pertussis toxin-sensitive increase in PMN cytosolic calcium analogous to that observed with Galphai coupled receptors. Other prominent motifs identified included phage bearing the consensus DLXTSK(M/L)X(V/I/L), where X represents a non-conserved position. Phage with this motif bound exclusively to a sub population of human PMN that comprised approximately 50% of the total and did not elicit a calcium response. The binding of such phage to PMN was prevented by co-incubation with competing peptides displaying identical or similar sequences (IC50 range from 0.6 micromol/L to 50 micromol/L for DLXTSK and GPNLTG, respectively). We speculate that these techniques will be useful in identifying functional cell-specific binding motifs and contribute to the development of new therapeutic and diagnostic strategies in human disease. (+info)
Isolation and characterization of a human homologue of the latrophilin gene from a region of 1p31.1 implicated in breast cancer.
We have identified a region of chromosome 1p31.1 that shows high frequency loss of heterozygosity (LOH) in human breast cancer. This region forms part of a 7 Mb YAC/BAC contig. In order to identify candidate sequences, mutation of which might contribute to the development of disease, we have carried out mapping studies of ESTs localized to 1p31.1. This analysis, coupled with library screening and a modified 5' RACE-PCR strategy, resulted in the identification and characterization of a novel gene (LPHH1) which is located adjacent to the smallest region of overlapping loss (SRO) seen in tumours. The 4209 bp open reading frame of the 7 kb LPHH1 transcript encodes a peptide which shows approximately 65% identity to rat latrophilin, a G-coupled, seven span transmembrane protein, which binds alpha-latrotoxin. In the human sequence, whilst conservation of the transmembrane domain is high, the intra- and extracellular domains show two regions of variable structure, which are presumably generated by alternative splicing. Surprisingly, while expression of the rat gene is tightly restricted to neurological and perhaps some endocrine cells, the human sequence appears to be expressed very widely in all normal tissues tested. Northern and RT-PCR analysis of a panel of tumour cell lines showed that LPHH1 expression was variable, apparently elevated in some lines and absent or markedly reduced in others. Furthermore, characterization of the range of transcripts encoded in a breast tumour cell line, compared to normal breast, suggested that gene product variability was higher in the tumour. (+info)