Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The surface of extracellular merozoites of P. knowlesi is covered with a coat 15-20 nm thick, made up of clusters of filaments standing erect on the plasma membrane. Filaments have stems 2 nm thick, the peripheral ends of which are complex, branching or ending in long trailing threads. Coat filaments occur on the surface of the parasite in regular rows at an early schizont stage, and persist until well after merozoite release. They are sensitive to trypsin and papain, and bind ethanolic phosphotungstate, indicating a proteinaceous nature. They are also removed by exposure to phosphate-buffered saline. Filaments bear negative charges, binding cationised ferritin throughout the depth of the coat and staining with ruthenium red. They cover the whole merozoite surface and mediate intercellular adhesion at distances of 15-150 nm, membrane to membrane. It is suggested that these filaments correspond to a major merozoite surface protein, and are important in the initial capture of red cells.
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PMID:Structure and development of the surface coat of erythrocytic merozoites of Plasmodium knowlesi. 374 63

The choriocapillaris is one example of a capillary bed lined by a fenestrated endothelium that is restrictive to exogenous tracers and endogenous plasma proteins. In this study we have examined the distribution of cell-surface monosaccharides utilizing biotinylated lectin-avidin ferritin cytochemistry. Receptors for wheat germ agglutinin were localized to the plasmalemma and diaphragms of some fenestrae, vesicles, and channels at the luminal endothelial front in amounts greater than seen for the other lectins employed. The absence of labeling following inhibition with N-acetylglucosamine and after tissue digestion with N-acetylhexosaminidase, but not after neuraminidase indicated that this lectin marked N-acetylglucosamine residues and not sialic acid. Wheat germ agglutinin receptors were not affected by pronase E or trypsin digestion, but were partially removed by proteinase K. The latter also removed many fenestral diaphragms. Wheat germ agglutinin receptors were cleaved with endoglycosidase D. The combined results indicate that the wheat germ agglutinin receptor is of the low-mannose type and part of a protein with hydrophobic properties. Receptors for concanavalin A (mannose) and Ricinus communis agglutinin (galactose) were also localized to the plasmalemma and endothelial diaphragms. The examination of sections at different tilt angles revealed that these lectins bound to the endothelium in a non-random distribution, encircling diaphragms of fenestrae and channels. Soybean agglutinin (N-acetylgalactosamine) marked endothelial structures sparsely. Following digestion with pronase E or trypsin, receptor sugars for the latter three lectins were completely removed, indicating their presence on protease susceptible glycoproteins. These findings demonstrate that the endothelium of the choriocapillaris bears carbohydrate moieties that are different than those described for permeable fenestrated endothelia.
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PMID:The cell surface of a restrictive fenestrated endothelium. I. Distribution of lectin-receptor monosaccharides on the choriocapillaris. 394 19

Three human cell lines from adenocarcinomas of the extrahepatic biliary tract were established in permanent tissue culture. Mz-ChA-1 and Mz-ChA-2 were cultured from mechanically dissociated gallbladder adenocarcinoma metastases and SK-ChA-1 was grown from malignant ascites of a patient with primary adenocarcinoma of the extrahepatic biliary tree. Cell doubling times in tissue culture are 3-4 days for Mz-ChA-1 and approximately 2 days for Mz-ChA-2 and SK-ChA-1. All three tumour cell lines were successfully transplanted to nude mice, inducing progressive tumour growth. Histologically, nude mouse tumours resembled the original adenocarcinomas. In vitro formation of gland-like structures were regularly seen in Mz-ChA-1 and Mz-ChA-2 but only occasionally in SK-ChA-1. All three cell lines formed contacts through interdigitating processes with desmosomes and junctional complexes. On scanning electron microscopy, an abundance of microvilli was seen at the cell surfaces. Chromosome analyses of all three tumour cell lines showed a wide range of numerical abnormalities and presence of marker chromosomes. Mz-ChA-1 appears to be highly differentiated with cells producing mucus. Mz-ChA-2 synthesizes components of complement C2, C3 and C5, while Mz-ChA-1 and SK-ChA-1 produce only C3 in detectable quantities. In addition, Mz-ChA-2 supernatants are positive for ferritin and alpha 1-fetoprotein, but not CEA; while Mz-ChA-1 and SK-ChA-1 produce only CEA. Supernatants of all three cell lines are positive for N-acetyl neuraminic acid (NANA), phosphohexoisomerase (PHI) and LDH, and negative for alpha 2-macroglobulin, alpha 1-anti-trypsin, gamma-GT, AP, coeruloplasmin, haptoglobin and albumin. A high cloning efficiency renders these new tumour cell lines suitable for continued studies on clonal heterogeneity in malignant tumours. The establishment of these cell lines in tissue culture facilitates further studies on the biology of upper gastrointestinal tract cancer in man.
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PMID:Biliary adenocarcinoma. Characterisation of three new human tumor cell lines. 405 57

The articular surface of adult BALB/c mouse femoral heads is covered by a fine granular electron dense material containing negative charges that bind electrostatically cationized ferritin. The material is of proteidic nature being digested by trypsin and chymopapain and resistant to testicular and microbial hyaluronidase, keratanase, chondroitinase ABC and AC. Mammalian collagenase disrupted the surface without digesting the material and allowed the penetration of cationized ferritin in the subsurface layers, where the label was bound on residual fibers. Sequential digestion with collagenase and chondroitinase ABC showed that the charges associated with the subsurface fibers are proteoglycans.
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PMID:Effects of enzymatic digestions on the negative charge of articular cartilage surfaces. 408 65

The distribution of specific glycoprotein receptors on the external surfaces of red cells was mapped, by the freeze-etching technique, to determine if the receptors coincided with the underlying 75-A intramembranous particles. Phytohemagglutinin, ferritin-conjugated phytohemagglutinin, and influenza virus were used as labeling agents since they can be seen by freeze-etching techniques and each reacts with a different site on the same glycoprotein molecule. The distribution of these labels was studied on intact human red cells, isolated ghost membranes, and trypsin-treated ghost membranes. The results show that the receptors for these labels are distributed uniformly over the surfaces of normal red cell membranes in the same apparent distribution as that of the 75-A particles within the membrane. The association between the external receptors and the underlying particles is especially evident when trypsin-treated ghost membranes are labeled: the labeled receptor sites and the intramembranous particles both form sharply defined, reticulated networks, which overlap. These results provide further support for the idea that membrane-bound glycoproteins are oriented so that their carbohydrate-rich segments, which bear the antigenic sites and receptors, are exposed to the external medium, while hydrophobic segments of the same molecules interact with lipids, and possibly other proteins, to form the intramembranous particles.
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PMID:The structure of erythrocyte membranes studied by freeze-etching. II. Localization of receptors for phytohemagglutinin and influenza virus to the intramembranous particles. 502 37

The presence of M antigens on group A streptococci is associated with hairlike fimbriae that cover the surface of the streptococcal cell wall and are demonstrable by electron microscopy. These fimbriae also may be associated with R antigen. Like M protein, the surface fimbriae are destroyed by trypsin treatment and reappear when "trypsinized" streptococci are reincubated in fresh, trypsin-free broth. Ferritin-conjugated, type-specific antibodies localize on homologous M+ cells in a pattern suggestive of several M antigenic sites along the length of individual surface fimbria. The M-associated fimbriae remain on the residual cell wall after removal of the bulk of group-specific polysaccharide through nitrous acid extraction. This suggests attachment of the fimbriae to the mucopeptide and minor polysaccharide components remaining in the nitrous acid-extracted wall. The pattern of localization of ferritin-conjugated antibodies on homologous streptococci before and after trypsin exposure and upon reincubation of the trypsinized cells in fresh medium suggests the following hypothesis: M antigen is secreted by the cell, is partially excreted through the otherwise intact cell wall, and is bound by the wall so that M protein occupies a peripheral, exposed position on the surfaces of the streptococcal cell wall.
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PMID:Electron microscopic studies on streptococci. I. M antigen. 534 94

We succeeded in an establishment of a human pancreatic cancer cell line (PK-1) from liver metastasis of pancreatic cancer. Primary pancreatic cancer cells grew as islands surrounded by fibroblastic cells. However, these fibroblastic cells were gradually omitted by the polygonal shaped cancer cells. This cell line contained neither zymogen granules nor trypsin indicating that this pancreatic cancer originated from pancreatic duct cells. Modal chromosome numbers of this cell line were 42 and 72 and the doubling time was 48 hr. This cell line was transplantable in athymic nude mice to form progressive tumors which had histology similar to that of the original cancer (papillotubular adenocarcinoma). Neither AFP nor ferritin but CEA was detected on the surface and in the cytoplasm of this cell line in indirect immunofluorescence. Rabbit antiserum against this pancreatic cancer cell line detected pancreatic cancer associated antigen besides CEA in the culture supernatant. This antiserum reacted with sera from patients with pancreatic cancer to form a distinct precipitin line in agarose gel which fused with the precipitin line formed between the culture supernatant of this cell line and the antiserum.
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PMID:Establishment of a human pancreatic cancer cell line and detection of pancreatic cancer associated antigen. 620 69

Mycoplasma pneumoniae initiates infection in the human host by attachment to respiratory epithelium. The organism attaches by a specialized terminal structure. Monoclonal antibodies to an organism surface protein (P1) inhibited attachment to respiratory epithelium and were localized to the tip structure by a ferritin antibody label. The P1 protein was degraded by trypsin treatment to smaller polypeptides that possessed the same antigenic determinants as the larger P1 protein when reacted with the specific monoclonal antibody, and evidence has been provided for the existence of multiple antigenic determinants on the attachment protein.
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PMID:Location of attachment moiety on Mycoplasma pneumoniae. 620 59

The appearance and continuing growth of extracellular material on Streptococcus mutans HS6 cells in sucrose-containing Merthiolated buffer was observed in a scanning electron microscope and was found to be related to the glucan synthesis on the cell and to adherence of the cell to a smooth surface. Cells grown in broth completely deprived of sucrose by invertase (HS6-IV) had a characteristic, slightly rugged surface structure. On incubation of HS6-IV in the sucrose-containing buffer, a few small globular particles appeared on the surface and grew to an irregular shape (globular to fibrilar) after several hours. The increase in the total glucan content of the cells paralleled the growth of the globular material, to which ferritin-conjugated anti-dextran globulin was found to bind. On the cell surface of cells harvested from conventional broth, both small globular and irregular structures, which possibly formed from sucrose in the broth, existed originally and continued to grow during incubation, along with the material newly appearing on the surface. The accumulation of glucan on the cells resulted in their adherence to a glass surface. The inhibition of growth of the extracellular material on the cells by trypsin, dextranase or anti-glucosyltransferase corresponded to the decrease in glucan synthesis and the loss of adhering ability. These results indicated that the material growing on the cell surface was glucan synthesized by glucosyltransferases.
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PMID:Synthesis of glucan on the cell surface of Streptococcus mutans: chemical and scanning electron microscopic studies. 621 5

To ascertain the directionality of chitin synthesis by yeast plasma membranes, the external surface of Saccharomyces cerevisiae protoplasts was labeled with ferritin--concanavalin A. After protoplast lysis, plasma membranes were isolated and treated with trypsin to activate chitin synthase (UDP-2-acetamido-2-deoxy-D-glucose:chitin 4-beta-acetamidodeoxy-D-glucosyl-transferase, EC 2.4.1.16). The membranes were then enrobed in agar and allowed to synthesize chitin from UDP-N-acetylglucosamine. After fixation and embedding in Epon, thin sections were stained for chitin with wheat germ agglutinin--colloidal gold complexes. The chitin marker was found near the ferritin-labeled external face of the membrane--i.e., the polysaccharide was located on the outside of the membrane, as it is in the intact cell. Chitin synthase activity was not detected in intact protoplasts before or after treatment with trypsin. The enzyme became available to trypsin activation after lysis of the protoplasts. Together with similar, previously reported experiments on the inactivation of chitin synthase by glutaraldehyde, these results indicate that the enzyme faces the interior of the cell. We conclude that, both in vivo and in vitro, the synthase receives N-acetylglucosamine residues from UDP-N-acetylglucosamine at the cytoplasmic face of the membrane and transfers them vectorially to a growing chain of chitin that is concomitantly extruded to the outside.
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PMID:Vectorial synthesis of a polysaccharide by isolated plasma membranes. 622 77


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