| 1. |
- Creamer, Lawrence K, et al.
(författare)
-
Heat-Induced Redistribution of Disulfide Bonds in Milk Proteins. 1. Bovine beta-Lactoglobulin
- 2004
-
Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 52:25, s. 7660-7668
-
Tidskriftsartikel (refereegranskat)abstract
- Changes in the structure and chemistry of -lactoglobulin (-LG) play an important role in the processing and functionality of milk products. In model -LG systems, there is evidence that the aggregates of heated -LG are held together by a mixture of intermolecular non-covalent association and heat-induced non-native disulfide bonds. Although a number of non-native disulfide bonds have been identified, little is known about the initial inter- and intramolecular disulfide bond rearrangements that occur as a result of heating. These interchange reactions were explored by examining the products of heat treatment to determine the novel disulfide bonds that form in the heated -LG aggregates. The native protein and heat-induced aggregates were hydrolyzed by trypsin, and the resulting peptides, before and after reduction with dithiothreitol, were separated by high-performance liquid chromatography and their identities confirmed by electrospray ionization mass spectrometry. Comparisons of these peptide patterns showed that some of the Cys160 was in the reduced form in heated -LG aggregates, indicating that the Cys160-Cys66 disulfide bond had been broken during heating. This finding suggests that disulfide bond interchange reactions between -LG non-native monomers, or polymers, and other proteins could occur largely via Cys160.
|
|
| 2. |
- Buffoni Hall, Roberta, et al.
(författare)
-
Water- and temperature-dependence of DNA damage and repair in the fruticose lichen Cladonia arbuscula ssp mitis exposed to UV-B radiation
- 2003
-
Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317. ; 118:3, s. 371-379
-
Tidskriftsartikel (refereegranskat)abstract
- The induction of cyclobutane pyrimidine dimers (CPDs) by ultraviolet-B radiation (UV-B, 280-315 nm) and repair mechanisms were studied in the lichen Cladonia arbuscula ssp. mitis exposed to different temperatures and water status conditions. In addition, the development and repair of CPDs were studied in relation to the different developmental stages of the lichen thallus podetial branches. Air-dried lichen thalli exposed to UV-B radiation combined with relatively high visible light (HL, 800 mumol m(-2) s(-1); 400-700 nm) for 7 days showed a progressive increase of CPDs with no substantial repair, although HL was present during and after irradiation with UV-B. Fully hydrated lichen thalli, that had not been previously exposed to UV-B radiation for 7 days, were given short-term UV-B radiation treatment at 25degreesC, and accumulated DNA lesions in the form of CPDs, with repair occurring when they were exposed to photoreactivating conditions (2 h of 300 mumol m(-2)s(-1), 400-700 nm). A different pattern was observed when fully hydrated thalli were exposed to short-term UV-B radiation at 2degreesC, in comparison with exposure at 25degreesC. High levels of CPDs were induced at 2degreesC under UV-B irradiation, without significant repair under subsequent photoreactivating light. Likewise, when PAR (300 mumol m(-2)s(-1) ) and UV-B radiation were given simultaneously, the CPD levels were not lowered. Throughout all experiments the youngest, less differentiated parts of the lichen thallus - namely 'tips', according to our arbitrary subdivision - were the parts showing the highest levels of CPD accumulation and the lowest levels of repair in comparison with the older thallus tissue ('stems'). Thus the experiments showed that Cladonia arbuscula ssp. mitis is sensitive to UV-B irradiation in the air-dried state and is not able to completely repair the damage caused by the radiation. Furthermore, temperature plays a role in the DNA damage repairing capacity of this lichen, since even when fully hydrated, C. arbuscula ssp. mitis did not repair DNA damage at the low temperatures.
|
|
| 3. |
- Creamer, L K, et al.
(författare)
-
Effect of genetic variation on the tryptic hydrolysis of bovine beta-lactoglobulin A, B, and C
- 2004
-
Ingår i: Journal of Dairy Science. - 1525-3198. ; 87:12, s. 4023-4032
-
Tidskriftsartikel (refereegranskat)abstract
- The structure, stability, and hydrolysis characteristics of beta-lactoglobulin (LG) A are different from those of either beta-LG B or beta-LG C. Purified samples of these proteins were hydrolyzed with trypsin and the rates of loss of native monomeric beta-LG structure were measured using sodium dodecyl sulfate PAGE. At the same time, the appearance of many individual peptides were identified and followed in time by HPLC, measuring their concentration as a function of solution pH, temperature, protein concentration, and added urea or palmitate. The identity of the peptides was confirmed by liquid chromatography-mass spectrometry. This semiquantitative exploration showed that the rate of hydrolysis was in the order beta-LG A > beta-LG B > beta-LG C under most circumstances, and that 12 of the 18 trypsin-susceptible bonds were cleaved at very similar rates that were governed by the variant type. Consequently, the rate of hydrolysis of the intact protein was related to the overall structural stability of the individual proteins and the accessibility of certain peptide bonds to the enzyme. The hydrolysis of mixtures of 2 or more variants or of denatured beta-LG gave more heterogeneous peptide mixtures.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Paulsson, K M, et al.
(författare)
-
Distinct differences in association of MHC class I with endoplasmic reticulum proteins in wild-type, and beta 2-microglobulin- and TAP-deficient cell lines
- 2001
-
Ingår i: International Immunology. - : Oxford University Press (OUP). - 0953-8178 .- 1460-2377. ; 13:8, s. 73-1063
-
Tidskriftsartikel (refereegranskat)abstract
- In this study we have compared the interaction of human MHC class I molecules with IgG heavy chain (HC) binding protein (BiP), calnexin, calreticulin, tapasin and TAP in beta(2)-microglobulin (beta(2)m)- or TAP-deficient cells, as well as in wild-type B-LCL cells. Distinct differences between the association of HC and these endoplasmic reticulum (ER) proteins were found in the three cell lines. In the absence of beta(2)m (Daudi cells), HC associated with both BiP and calnexin. A prominent portion of HC was complexed simultaneously to both chaperones, as indicated by co-precipitation with either anti-calnexin or anti-class I antisera. In the presence of beta(2)m, but absence of TAP (T2 cells), HC could be co-precipitated with calnexin, whereas no detectable interaction with BiP could be demonstrated. This suggests that calnexin interacts with HC at a later stage than BiP. In B-LCL cells, HC-beta(2)m associated with calreticulin and tapasin, whereas no interaction with calnexin and BiP was observed. In the absence of beta(2)m, HC were rapidly degraded in the ER, while the ER retained HC were stabilized in the presence of beta(2)m, even in the absence of TAP. The dissociation of class I molecules from TAP in B-LCL cells correlated with the kinetics of appearance of class I molecules on the cell surface, suggesting that TAP retains peptide-free class I molecules in the ER. Taken together, our results suggest the model that BiP and calnexin sequentially control the folding of MHC class I, before MHC class I molecules associate with the loading complex.
|
|
| 8. |
- Wang, P, et al.
(författare)
-
Inhibition of the transcription factors AP-1 and NF-kappaB in CD4 T cells by peroxisome proliferator-activated receptor gamma ligands
- 2001
-
Ingår i: International Immunopharmacology. - 1567-5769. ; 1:4, s. 12-803
-
Tidskriftsartikel (refereegranskat)abstract
- The peroxisome proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor superfamily, is essential for adipocyte differentiation and glucose homeostasis. PPARgamma has been found recently to regulate macrophage activation in response to mitogens and inflammation. Our study shows PPARgamma to be preferentially expressed in the nuclei of resting T cells and to increase upon activation of T cells by either anti-CD3 and anti-CD28 or phorbol myristyl acetate (PMA). We also found the PPARgamma ligand ciglitizone to attenuate the activation of T cells by inhibiting cytokine gene expression and anti-CD3 and anti-CD28 or PMA-induced proliferative responses. Inhibition of both the proliferative response and inflammatory cytokine expression in CD4 T cells was correlated with suppression of the activated transcription factors AP1 and NF-kappaB. PPARgamma ligands also strongly inhibited SEA-induced Vbeta3 T cell activation in vivo. These results, together with previous findings of the inhibitory effect of PPARgamma ligands on activated macrophages, provide clear evidence for PPARgamma as a negative regulator of the inflammatory activation of both macrophage and T cells. PPARgamma may thus be a potential therapeutic target for the treatment of autoimmunity.
|
|
| 9. |
|
|
