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31.
The solution structure of human beta2-microglobulin reveals the prodromes of its amyloid transition
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Verdone G Corazza A Viglino P Pettirossi F Giorgetti S Mangione P Andreola A Stoppini M Bellotti V Esposito G 《Protein science : a publication of the Protein Society》2002,11(3):487-499
The solution structure of human beta2-microglobulin (beta2-m), the nonpolymorphic component of class I major histocompatibility complex (MHC-I), was determined by (1)H NMR spectroscopy and restrained modeling calculations. Compared to previous structural data obtained from the NMR secondary structure of the isolated protein and the crystal structure of MHC-I, in which the protein is associated to the heavy-chain component, several differences are observed. The most important rearrangements were observed for (1) strands V and VI (loss of the C-terminal and N-terminal end, respectively), (2) interstrand loop V-VI, and (3) strand I, including the N-terminal segment (displacement outward of the molecular core). These modifications can be considered as the prodromes of the amyloid transition. Solvation of the protected regions in MHC-I decreases the tertiary packing by breaking the contiguity of the surface hydrophobic patches at the interface with heavy chain and the nearby region at the surface charge cluster of the C-terminal segment. As a result, the molecule is placed in a state in which even minor charge and solvation changes in response to pH or ionic-strength variations can easily compromise the hydrophobic/hydrophilic balance and trigger the transition into a partially unfolded intermediate that starts with unpairing of strand I and leads to polymerization and precipitation into fibrils or amorphous aggregates. The same mechanism accounts for the partial unfolding and fiber formation subsequent to Cu(2+) binding, which is shown to occur primarily at His 31 and involve partially also His 13, the next available His residue along the partial unfolding pathway. 相似文献
32.
Plant secondary compounds are recognized deterrents and toxins to a variety of herbivores. The effect of secondary compounds on water balance of herbivores is virtually unexplored, yet secondary compounds could potentially cause a decrease in an animal's ability to maintain water balance. We investigated the effects of secondary compounds, alpha-pinene and creosote resin, on water balance in three species of herbivorous woodrats (Neotoma stephensi, N. albigula, N. lepida). In separate experiments, we measured the effect of these secondary compounds on voluntary water consumption, urine volume and urine osmolarity. In both experiments, water intake and urine volume increased and urine osmolarity decreased compared to controls. Water balance of specialist or experienced woodrats was less affected than generalists and woodrats with less prior experience with particular secondary compounds. Our results suggest that secondary compounds have diuretic-like effects on herbivores. Woodrats live in arid habitats with limited access to freestanding water; thus an increase in water requirements may have profound consequences on foraging behavior and fitness. 相似文献
33.
Acceptor specificity of the human leukocyte alpha3 fucosyltransferase: role of FucT-VII in the generation of selectin ligands 总被引:2,自引:2,他引:0
Britten CJ; van den Eijnden DH; McDowell W; Kelly VA; Witham SJ; Edbrooke MR; Bird MI; de Vries T; Smithers N 《Glycobiology》1998,8(4):321-327
The alpha3 fucosyltransferase, FucT-VII, is one of the key
glycosyltransferases involved in the biosynthesis of the sialyl Lewis X
(sLex) antigen on human leukocytes. The sialyl Lewis X antigen
(NeuAcalpha(2-3)Galbeta(1-4)[Fucalpha(1-3)]GlcNAc-R) is an essential
component of the recruitment of leukocytes to sites of inflammation,
mediating the primary interaction between circulating leukocytes and
activated endothelium. In order to characterize the enzymatic properties of
the leukocyte alpha3 fucosyltransferase FucT-VII, the enzyme has been
expressed in Trichoplusia ni insect cells. The enzyme is capable of
synthesizing both sLexand sialyl-dimeric-Lexstructures in vitro , from
3'-sialyl-lacNAc and VIM-2 structures, respectively, with only low levels
of fucose transfer observed to neutral or 3'-sulfated acceptors. Studies
using fucosylated NeuAcalpha(2-3)-(Galbeta(1- 4)GlcNAc)3-Me acceptors
demonstrate that FucT-VII is able to synthesize both di-fucosylated and
tri-fucosylated structures from mono- fucosylated precursors, but
preferentially fucosylates the distal GlcNAc within a polylactosamine
chain. Furthermore, the rate of fucosylation of the internal GlcNAc
residues is reduced once fucose has been added to the distal GlcNAc. These
results indicate that FucT-VII is capable of generating complex selectin
ligands, in vitro , however the order of fucose addition to the lactosamine
chain affects the rate of selectin ligand synthesis.
相似文献
34.
David A Baldwin Deolinda MR de Sousa 《Biochemical and biophysical research communications》1981,99(4):1101-1107
The kinetics of iron release from N-terminal and C-terminal monoferric human transferrins has been studied using EDTA as the accepting chelate. In the absence of added salts iron release from the N-terminal site is more facile but the relative lability can be reversed by the addition of NaClO4, NaCl and LiCl. The results indicate that both anions and cations can affect the lability of the two sites. Since the relative lability of the two monoferrictransferrins is affected by fairly moderate concentrations of NaCl and NaClO4 we suggest that the ionic composition serum may play an important role in determining the observed distribution of iron among the sites. A new method for the preparation of N-terminal monoferrictransferrin is described. 相似文献
35.
The synthesis of the title compound was achieved in seven steps and 61% overall yield from methyl alpha-D-glucopyranoside. 相似文献
36.
Sianos G Kay IP Carlier SG Lighart JM Wardeh AJ Coen VL Levendag PC Serruys PW 《International journal of cardiovascular interventions》2000,3(2):121-125
The application of beta-radiation in coronary arteries is a promising new technique for the treatment of in-stent restenosis. This is the first case in which the 5 F. delivery catheter of the Beta-Cath trade mark system was advanced through the struts of a stent, previously deployed in an adjacent branch, so as to deliver radiation to the target vessel. 相似文献
37.
Giorgetti S Rossi A Mangione P Raimondi S Marini S Stoppini M Corazza A Viglino P Esposito G Cetta G Merlini G Bellotti V 《Protein science : a publication of the Protein Society》2005,14(3):696-702
It has been claimed that beta2-microglobulin (beta2-m) interacts with type I and type II collagen, and this property has been linked to the tissue specificity of the beta2-m amyloid deposits that target the osteo-articular system. The binding parameters of the interaction between collagen and beta2-m were determined by band shift electrophoresis and surface plasma resonance by using bovine collagen of type I and type II and various isoforms of beta2-m. Wild-type beta2-m binds collagen type I with a Kd of 4.1 x 10(-4) M and type II with 2.3 x 10(-3) M. By the BIAcore system we monitored the binding properties of the conformers of the slow phase of folding of beta2-m. The folding intermediates during the slow phase of folding do not display any significant difference with respect to the binding properties of the fully folded molecule. The affinity of beta2-m truncated at the third N-terminal residue does not differ from that reported for the wild-type protein. Increased affinity for collagen type I is found in the case of N-terminal truncated species lacking of six residues. The Kd of this species is 3.4 x 10 (-5) M at pH 7.4 and its affinity increases to 4.9 x 10(-6) M at pH 6.4. Fluctuations of the affinity caused by beta2-m truncation and pH change can cause modifications of protein concentration in the solvent that surrounds the collagen, and could contribute to generate locally a critical protein concentration able to prime the protein aggregation. 相似文献
38.
Jo?o?Luiz?S?Moreira Rodrigo?M?Mota Maria?F?Horta Santuza?MR?Teixeira Elisabeth?Neumann Jacques?R?Nicoli álvaro?C?NunesEmail author 《BMC microbiology》2005,5(1):15
Background
The accurate identification of Lactobacillus and other co-isolated bacteria during microbial ecological studies of ecosystems such as the human or animal intestinal tracts and food products is a hard task by phenotypic methods requiring additional tests such as protein and/or lipids profiling. 相似文献39.
The aim of this study is determining the different patterns of egg nests and the morphological differences between the specimens of Cicadatra persica Kirkalidy, 1909 (Hemiptera: Cicadidae) distributed in fruit orchards in Erneh located on AL-Sheikh mountain south west of Syria. The appearance of 80 egg nests was studied, and the results showed that there were two basic patterns of egg nests laid by Cicadatra persica, 90% of the egg nests were of the first pattern (consists of several adjacent slits), while 10% of them were of the second pattern (consists of several divergent slits). A random sample consisting of 300 specimens (150 males and 150 females) were also studied concentrating on the differences in the color of the supra-antennal plate and in the number of spurs on the tibia of the hind legs. The results showed that there were two basic patterns of individuals based on the differences in the color of supra-antennal plate. The first pattern (individuals with yellow supra-antennal plates), constituted more than 90%, and the second one (individuals with black supra-antennal plates) constituted less than 10%. The results also showed that there were 27 different patterns based on the number of spurs on the tibia of the hind legs. One of them was a common pattern (2, 3) whose individuals have 2 spurs on the upper side of the tibia of the hind legs and 3 spurs on the lateral side of the tibia of the hind legs. The total percent of this common pattern was 76%. The other 26 patterns were different from each other, and the total percent of all these different patterns was 24%. 相似文献
40.
MR D'Andrea 《Biotechnic & histochemistry》2013,88(2):55-64
Reliable immunohistochemical detection of collagen in formalin fixed, paraffin embedded tissues requires protease digestion. While these pan-proteases (pepsin, trypsin, protease K, etc.) enhance collagen detection, they also digest many other tissue proteins and produce poor cellular morphology and unrecognizable cellular structures. Balancing the conditions (protease type, concentration, incubation time and temperature) to digest some, but not all, proteins in a tissue section while optimizing collagen detection requires one to compromise improved collagen immunolabeling with adequate cellular morphology. Furthermore, optimal conditions for digesting tissue proteins to enhance collagen detection vary among tissue types and their fixation. Although brain is not typically subject to these deleterious consequences, structures such as epithelium, spermatids, stroma etc. and other tissues with complicated histology are profoundly affected. To resolve this technical dilemma, we discovered a novel use for collagenase to enhance collagen immunodetection without affecting the noncollagen proteins, thereby preserving tissue morphology. Collagenase, which is typically used in vitro for disassociation of cells, has never been used reliably on formalin fixed, paraffin embedded tissue sections. This new use of collagenase for immunohistochemistry promotes increased collagen immunolabeling, is easy to use, is versatile, and allows preservation of tissue structure that provides maximal and accurate histological information. 相似文献