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21.
Rick PD; Hubbard GL; Kitaoka M; Nagaki H; Kinoshita T; Dowd S; Simplaceanu V; Ho C 《Glycobiology》1998,8(6):557-567
The polysaccharide chains of enterobacterial common antigen (ECA) consist
of linear trisaccharide repeat units with the structure -->3)-
alpha-d-Fuc4NAc-(1-->4)-beta-d-ManNAcA-(1-->
4)-alpha-d-GlcNAc-(1-->, where Fuc4NAc is 4-acetamido-4,
6-dideoxy-d-galactose, ManNAcA is N - acetyl-d- mannosaminuronic acid, and
GlcNAc is N -acetyl-d-glucosamine. The major form of ECA (ECAPG) consists
of polysaccharide chains that are believed to be covalently linked to
diacylglycerol through phosphodiester linkage; the phospholipid moiety
functions to anchor molecules in the outer membrane. The ECA trisaccharide
repeat unit is assembled as a polyisoprenyl-linked intermediate which has
been tentatively identified as Fuc4NAc-ManNAcA-GlcNAc-
pyrophosphorylundecaprenol (lipid III). Subsequent chain-elongation
presumably occurs by a block-polymerization mechanism. However, the
identity of the polyisoprenoid carrier-lipid has not been established.
Accordingly, the current studies were conducted in an effort to
structurally characterize the polyisoprenyl lipid-carrier involved in ECA
synthesis. Isolation and characterization of the lipid carrier was
facilitated by the accumulation of a ManNAcA-GlcNAc-
pyrophosphorylpolyisoprenyl lipid (lipid II) in mutants of Salmonella
typhimurium defective in the synthesis of TDP-Fuc4NAc, the donor of Fuc4NAc
residues for ECA synthesis. Analyses of lipid II preparations by fast atom
bombardment tandem mass spectroscopy (FAB-MS/MS) resulted in the
identification of the lipid-carrier as the 55-carbon polyisoprenyl alcohol,
undecaprenol. These analyses also resulted in the identification of a novel
glycolipid which copurified with lipid II. FAB-MS/MS analyses of this
glycolipid revealed its structure to be 1,2-diacyl- sn
-glycero-3-pryophosphoryl-GlcNAc-ManNAcA (DGP- disaccharide). An
examination of purified ECAPGby phosphorus-31 nuclear magnetic resonance
spectroscopy confirmed that the polysaccharide chains are linked to
diacylglycerol through phosphodiester linkage. Thus, DGP-disaccharide does
not appear to be an intermediate in ECAPGsynthesis. Nevertheless, although
the available evidence clearly indicate that lipid II is a precursor of
DGP-disaccharide, the function of this novel glycolipid is not yet known,
and it may be an intermediate in the biosynthesis of a molecule other than
ECAPG.
相似文献
22.
角质形成细胞生长因子(KGF)在喉粘膜良性、癌前及恶性病变中的mRNA水平分析 总被引:1,自引:0,他引:1
利用原位杂交的方法检测KGFmRNA在正常喉粘膜上皮(N)、慢性非特异性炎症(IF)、不典型增生(DYS)及鳞癌(SCC)中的转录水平,探讨KGF在喉粘膜良性及恶性病变中的分布和可能的作用。结果表明,KGFmRNA不仅在间质中的成纤维细胞中表达,少量的炎细胞及血管内皮细胞中亦表达,而且从N、IF、DYS到SCC、KGFmRNA转录水平逐渐增强;上皮细胞及肿瘤性上皮细胞不表达KGFmRNA,KGFmRNA在分化差的SCC周围间质中表达较分化好的SCC周围间质增多。结论:KGF在上皮与间充质细胞的交互作用中发挥着重要的作用,对维持喉粘膜正常结构、代谢及喉癌的发生发展具有重要意义。 相似文献
23.
Odunuga OO Longshaw VM Blatch GL 《BioEssays : news and reviews in molecular, cellular and developmental biology》2004,26(10):1058-1068
Molecular chaperones facilitate the correct folding of other proteins under physiological and stress conditions. Recently it has become evident that various co-chaperone proteins regulate the cellular functions of these chaperones, particularly Hsp70 and Hsp90. Hop is one of the most extensively studied co-chaperones that is able to directly associate with both Hsp70 and Hsp90. The current dogma proposes that Hop functions primarily as an adaptor that directs Hsp90 to Hsp70-client protein complexes in the cytoplasm. However, recent evidence suggests that Hop can also modulate the chaperone activities of these Hsps, and that it is not dedicated to Hsp70 and Hsp90. While the co-chaperone function of Hop within the cytoplasm has been extensively studied, its association with nuclear complexes and prion proteins remains to be elucidated. This article will review the structural features of Hop, and the evidence that its biological function is considerably broader than previously envisaged. 相似文献
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Molecular chaperones have been used for the improved expression of target proteins within heterologous systems; however, the chaperone and target protein have seldom been matched in terms of origin. We have developed a heterologous co-expression system that allows independent expression of the plasmodial chaperone, PfHsp70, and a plasmodial target protein. In this study, the target was Plasmodium falciparum GTP cyclohydrolase I (PfGCHI), the first enzyme in the plasmodial folate pathway. The sequential expression of the molecular chaperone followed by the target protein increased the expression of soluble functional PfGCHI. His-tagged PfGCHI was successfully purified using nickel affinity chromatography, and the specific activity was determined by high performance liquid chromatography with spectrofluorometeric detection to be 5.93nmol/h/mg. This is the first report of a heterologous co-expression system in which a plasmodial chaperone is harnessed for the improved production and purification of a plasmodial target protein. 相似文献
28.
Taryn Bodill Anne C. Conibear Marius K.M. Mutorwa Jessica L. Goble Gregory L. Blatch Kevin A. Lobb Rosalyn Klein Perry T. Kaye 《Bioorganic & medicinal chemistry》2013,21(14):4332-4341
DOXP-reductoisomerase (DXR) is a validated target for the development of antimalarial drugs to address the increase in resistant strains of Plasmodium falciparum. Series of aryl- and heteroarylcarbamoylphosphonic acids, their diethyl esters and disodium salts have been prepared as analogues of the potent DXR inhibitor fosmidomycin. The effects of the carboxamide N-substituents and the length of the methylene linker have been explored using in silico docking studies, saturation transfer difference NMR spectroscopy and enzyme inhibition assays using both EcDXR and PfDXR. These studies indicate an optimal linker length of two methylene units and have confirmed the importance of an additional binding pocket in the PfDXR active site. Insights into the constraints of the PfDXR binding site provide additional scope for the rational design of DXR inhibitors with increased ligand–receptor interactions. 相似文献
29.
Cancer procoagulant is present only in malignant tumours and the undifferentiated tissues of human placenta. Its possible role in angiogenesis and metastasis was investigated. Cancer procoagulant increased the steady-state mRNA level of L1 cell adhesion molecule (L1CAM) in MCF-7 breast cancer cells and E14 mouse embryonic stem cells (MESCs), while an increase in angiogenin mRNA was observed in MDA-MB-231 breast cancer cells. Furthermore, production of vascular endothelial growth factor (VEGF) protein in MCF-7 breast cancer cells and E14 MESCs, but decreased in MDA-MB-231 breast cancer cells. We conclude that cancer procoagulant could potentially play a part in angiogenesis in cancer and vascular development during embryonic development. 相似文献
30.
Malaria is caused by Plasmodium species, whose transmission to vertebrate hosts is facilitated by mosquito vectors. The transition from the cold blooded
mosquito vector to the host represents physiological stress to the parasite, and additionally malaria blood stage infection
is characterised by intense fever periods. In recent years, it has become clear that heat shock proteins play an essential
role during the parasite's life cycle. Plasmodium falciparum expresses two prominent heat shock proteins: heat shock protein 70 (PfHsp70) and heat shock protein 90 (PfHsp90). Both of
these proteins have been implicated in the development and pathogenesis of malaria. In eukaryotes, Hsp70 and Hsp90 proteins
are functionally linked by an essential adaptor protein known as the Hsp70–Hsp90 organising protein (Hop). In this study,
recombinant P. falciparum Hop (PfHop) was heterologously produced in E. coli and purified by nickel affinity chromatography. Using specific anti-PfHop antisera, the expression and localisation of PfHop
in P. falciparum was investigated. PfHop was shown to co-localise with PfHsp70 and PfHsp90 in parasites at the trophozoite stage. Gel filtration
and co-immunoprecipitation experiments suggested that PfHop was present in a complex together with PfHsp70 and PfHsp90. The
association of PfHop with both PfHsp70 and PfHsp90 suggests that this protein may mediate the functional interaction between
the two chaperones. 相似文献