| 1. |
- Nordman, Henrik, et al.
(författare)
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Gastric MUC5AC and MUC6 are large oligomeric mucins which differ in size, glycosylation and tissue distribution
- 2002
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Ingår i: Biochemical Journal. - : The Biochemical Society. - 0264-6021 .- 1470-8728. ; 364, s. 191-200
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Tidskriftsartikel (refereegranskat)abstract
- Gastric MUC5AC and MUC6 mucins were studied using polyclonal antibodies. Immunohistochemistry showed MUC5AC to originate from the surface epithelium, whereas MUC6 was produced by the glands. Mucins from the surface epithelium or glands of corpus and antrum were purified using CsCl/4M guanidinium chloride density-gradient centrifugation. MUC5AC appeared as two distinct populations at 1.4 and 1.3 g/ml, whereas MUC6, which was enriched in the gland tissue, appeared at 1.45 g/ml. Reactivity with antibodies against the Le(b) structure (where Le represents the Lewis antigen) followed the MUC5AC distribution, whereas antibodies against the Le(y) structure and reactivity with the GlcNAc-selective Solanum tuberosum lectin coincided with MUC6, suggesting that the two mucins are glycosylated differently. Rate-zonal centrifugation of whole mucins and reduced subunits showed that both gastric MUC5AC and MUC6 are oligomeric glycoproteins composed of disulphide-bond linked subunits and that oligomeric MUC5AC was apparently smaller than MUC6. A heterogeneous population of 'low-density' MUC5AC mucins, which were smaller than the 'high-density' ones both before and after reduction, reacted with an antibody against a variable number tandem repeat sequence within MUC5AC, suggesting that they represent precursor forms of this mucin. Following ion-exchange HPLC, both MUC5AC and MUC6 appeared as several distinct populations, probably corresponding to 'glycoforms' of the mucins, the most highly charged of which were found in the gland tissue.
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| 2. |
- Shleev, Sergey, et al.
(författare)
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Electrochemical redox transformations of T1 and T2 copper sites in native Trametes hirsuta laccase at gold electrode
- 2005
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Ingår i: Biochemical Journal. - : Published by Portland Press on behalf of The Biochemical Society. - 0264-6021 .- 1470-8728. ; 385:Part 3, s. 745-754
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Tidskriftsartikel (refereegranskat)abstract
- Mediatorless, electrochemically driven, redox transformations of TI (type 1) and T2 copper sites in Trametes hirsuta laccase were studied by cyclic voltarnmetry and spectroclectrochernical redox titrations using bare gold electrode. DET (direct electron transfer) between I he electrode and the enzyme was observed under anaerobic conditions. From analysis of experimental data it is concluded that the T2 copper site is in DET contact with gold. It was found that electron transfer between the gold surface and the TI copper site progresses through the T2 copper site. From EPR measurements and electrochemical data it is proposed that the redox potential of the T2 site for high-potential 'blue' laccase is equal to about 400 mV versus NHE (normal hydrogen electrode) at pH 6.5. The hypothesis that the redox potentials of the T2 copper sites in low- and high-potentiai laccases/oxiclases from totally different sources might be very similar, i.e. approx. 400 mV, is discussed.
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| 3. |
- Wickström, Claes, et al.
(författare)
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Macromolecular organization of saliva : identification of ‘insoluble’ MUC5B assemblies and non-mucin proteins in the gel phase
- 2000
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Ingår i: Biochemical Journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 351:2, s. 421-428
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Tidskriftsartikel (refereegranskat)abstract
- Stimulated human submandibular’sublingual (HSMSL) and whole saliva were separated into sol and gel phases and mucins were isolated by density-gradient centrifugation in CsCl/4M guanidinium chloride. MUC5B and MUC7 were identified using anti-peptide antisera raised against sequences within the MUC5B and MUC7 apoproteins respectively. MUC7 was found mainly in the sol phase of both HSMSL and whole saliva, but some MUC7 was consistently present in the gel phase, suggesting that this mucin may interact with the salivary gel matrix. In HSMSL saliva, MUC5B was found in the gel phase ; however, most of the materialwas‘ insoluble ’inguanidiniumchlorideandwasonly brought into solution by reduction. In whole saliva, the MUC5B mucin was present both in the sol and gel phases although some materialwasagain‘ insoluble ’.Rate-zonalcentrifugationof whole saliva showed that MUC5B mucins in the sol phase were smaller than those in the gel phase, suggesting differences in oligomerization and/or degradation. Antibodies against IgA, secretory component, lysozyme and lactoferrin were used to study the distribution of non-gel-forming proteins in the different phases of saliva. The majority of these proteins was found in the sol phase of both HSMSL and whole saliva. However, a significant fraction was present in the gel phase of whole saliva, suggesting a post-secretory interaction with the salivary gel matrix. A monoclonal antibody against a parotid salivary agglutinin was used to show that this protein is present mainly in the gel phase of both whole saliva and parotid secretion.
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