Browsing by Subject "Glycosylation"

Now showing 1 - 3 of 3
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    Identification of a collagen type I adhesin of Bacteroides fragilis
    (Public Library of Science, 2014) Galvão, Bruna P G V; Weber, Brandon W; Rafudeen, Mohamed S; Ferreira, Eliane O; Patrick, Sheila; Abratt, Valerie R
    Bacteroides fragilis is an opportunistic pathogen which can cause life threatening infections in humans and animals. The ability to adhere to components of the extracellular matrix, including collagen, is related to bacterial host colonisation. Collagen Far Western analysis of the B. fragilis outer membrane protein (OMP) fraction revealed the presence two collagen adhesin bands of ∼31 and ∼34 kDa. The collagen adhesins in the OMP fraction were separated and isolated by two-dimensional SDS-PAGE and also purified by collagen affinity chromatography. The collagen binding proteins isolated by both these independent methods were subjected to tandem mass spectroscopy for peptide identification and matched to a single hypothetical protein encoded by B. fragilis NCTC 9343 (BF0586), conserved in YCH46 (BF0662) and 638R (BF0633) and which is designated in this study as cbp1 (collagen binding protein). Functionality of the protein was confirmed by targeted insertional mutagenesis of the cbp1 gene in B. fragilis GSH18 which resulted in the specific loss of both the ∼31 kDa and the ∼34 kDa adhesin bands. Purified his-tagged Cbp1, expressed in a B. fragilis wild-type and a glycosylation deficient mutant, confirmed that the cbp1 gene encoded the observed collagen adhesin, and showed that the 34 kDa band represents a glycosylated version of the ∼31 kDa protein. Glycosylation did not appear to be required for binding collagen. This study is the first to report the presence of collagen type I adhesin proteins in B. fragilis and to functionally identify a gene encoding a collagen binding protein.
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    Identification of N -Linked Glycosylation Sites in Human Testis Angiotensin-converting Enzyme and Expression of an Active Deglycosylated Form
    (1997) Yu, X Christopher; Sturrock, Edward D; Wu, Zhuchun; Biemann, Klaus; EHLERS, Mario R W; Riordan, James F
    The sites of glycosylation of Chinese hamster ovary cell expressed testicular angiotensin-converting enzyme (tACE) have been determined by matrix-assisted laser desorption ionization/time of flight/mass spectrometry of peptides generated by proteolytic and cyanogen bromide digestion. Two of the seven potential N-linked glycosylation sites, Asn90 and Asn109, were found to be fully glycosylated by analysis of peptides before and after treatment with a series of glycosidases and with endoproteinase Asp-N. The mass spectra of the glycopeptides exhibit characteristic clusters of peaks which indicate the N-linked glycans in tACE to be mostly of the biantennary, fucosylated complex type. This structural information was used to demonstrate that three other sites, Asn155, Asn337, and Asn586, are partially glycosylated, whereas Asn72 appears to be fully glycosylated. The only potential site that was not modified is Asn620. Sequence analysis of tryptic peptides obtained from somatic ACE (human kidney) identified six glycosylated and one unglycosylated Asn. Only one of these glycosylation sites had a counterpart in tACE. Comparison of the two proteins reveals a pattern in which amino-terminal N-linked sites are preferred. The functional significance of glycosylation was examined with a tACE mutant lacking the O-glycan-rich first amino-terminal 36 residues and truncated at Ser625. When expressed in the presence of the alpha-glucosidase I inhibitor N-butyldeoxynojirimycin and treated with endoglycosidase H to remove all but the terminal N-acetylglucosamine residues, it retained full enzymatic activity, was electrophoretically homogeneous, and is a good candidate for crystallographic studies.
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    Limited neutralizing antibody specificities drive neutralization escape in early HIV-1 subtype C infection
    (Public Library of Science, 2009) Moore, Penny L; Ranchobe, Nthabeleng; Lambson, Bronwen E; Gray, Elin S; Cave, Eleanor; Abrahams, Melissa-Rose; Bandawe, Gama; Mlisana, Koleka; Karim, Salim S Abdool; Williamson, Carolyn
    Author Summary Most HIV-1 infected individuals develop neutralizing antibodies against their own virus, termed an autologous neutralizing response. It is known that this response exerts pressure on the envelope of HIV, the target of such antibodies, resulting in neutralization escape. Here we have identified the targets of these antibodies and the precise genetic basis of neutralization escape in 4 individuals infected with HIV-1 subtype C. We show that V1V2 is commonly involved in escape, and that the C3 region is also a target in some cases. The latter observation confirms this region is exposed in subtype C, unlike subtype B. We show that neutralization escape is conferred by a few amino acid mutations, some of which are outside the antibody target site. Moreover, escape from these limited specificities even within a single individual occurs via a variety of different pathways involving substitutions, indels and glycan shifts. The finding in 2 individuals that an anti-C3 response developed first, followed by an anti-V1V2 response, suggests there may be specific regions of envelope particularly vulnerable to antibody neutralization. Overall, we propose a mechanistic explanation for how HIV-1 epitopes drive sequential waves of neutralization escape in early subtype C infection.