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Microorganisms have developed three different systems for catalyzing protein phosphorylation and using this reversible modification to regulate their cellular activities. The first classical system utilizes nucleoside-triphosphates as phosphoryl donors and leads to the modification of protein substrates at serine/threonine or tyrosine residues. The second system, called two-component system...
The selected-acceptor substrate peptide (TTSAPTTS), deduced from the human mucin gene MUC5AC (expressed essentially in the human gastric and tracheobronchial mucosa), was used to assay polypeptide:N-acetylgalactosaminyltransferases (GalNAc transferases) of different microsomal preparations, obtained from gastric and colonic mucosa in normal and tumoral situations. The O-glycosylated products, analyzed...
For the past 15 years, it has appeared increasingly evident that the N-glycosylation process was accompanied by the release of oligomannoside type oligosaccharides. This material is constituted of oligosaccharide-phosphates and of neutral oligosaccharides possessing one GlcNAc (OS-Gn1) or two GlcNAc (OS-Gn2) at the reducing end. It has been demonstrated that oligosaccharide-phosphates originated...
Lectins were evidenced on the surface of one Agrobacterium tumefaciens wild strain (82.139) by agglutination test and neoglycoprotein labelling. Bacteria were incubated in the presence of various fluorescein-labelled neoglycoproteins and the binding was assessed by a fluorimetric method. Among the fluorescein-labelled neoglycoproteins tested, the one bearing α-D-galactosyl residues was the most efficient...
Several kinds of natural fibrous proteins have been chosen as models: silk fibroin from Bombyx mori, silks from various species of spiders and collagens. The dragline silk of the spider Nephila clavipes is able to stretch by 30% before breaking and has a high tensile strength. It is stronger per unit weight than high tensile steel. Although the partial sequence of the two components of dragline...
Sialic acids can be acetylated at the 4, 7, 8 and/or 9 position. Biological roles of these substitutions have been missed until recently because of their low abundance and lability to conventional purification methods. The recent advances in the analysis of sialic acids have allowed to demonstrate that O-acetylation has a selective but widespread distribution. The metabolism of acetylated sialic...
We review the metabolism of specific sugars used for protein glycosylation, focusing on the fate of exogenously provided sugars. Theoretically, all glycoprotein sugars can derive from glucose, but previous studies show that other exogenous sugars can be incorporated into glycoproteins. From data obtained in congenital galactosemia, exogenous galactose may be important for correct glycosylation....
Conformational flexibility and structural fluctuations play an important role in enzyme activity. A great variety of internal motions ranging over different time scales and of different amplitudes are involved in the catalytic cycle. These different types of motions and their functional consequences are considered in the light of experimental data and theoretical analyses. The conformational changes...
Lectins are present on the surface of many cells. Many lectins actively recycle from membrane to endosomes and efficiently take up glycoconjugates in a sugar-dependent manner. On this basis, glycoconjugates, specially those obtained by chemical means, are good candidates as carriers of drugs, oligonucleotides or genes. In this paper, we present a panel of methods suitable to transform unprotected...
The G protein coupled receptors (GPCR) are an important class of proteins that act as signal transducers through the cytoplasmic membrane. Understanding the structure and activation mechanism of these proteins is crucial for understanding many different aspects of cellular signalling. The olfactory receptors correspond to the largest family of GPCRs. Very little is known about how the structures...
Atherosclerosis cardiovascular disease is the leading cause of death in industrial societies. For coronary heart disease, hypercholesterolemia and dyslipoproteinemia are the major risk factors. Low serum levels of cholesterol in the HDL fraction is the most common abnormality found in patients with confirmed coronary artery disease. A therapeutical strategy consists in increasing the serum HDL...
In animal species, spermiogenesis, the late stage of spermatogenesis, is characterized by a dramatic remodelling of chromatin which involves morphological changes and various modifications in the nature of the nuclear basic proteins. According to the evolution of species, three situations can be observed: a)_persistence of somatic histones or appearance of sperm-specific histones; b) direct replacement...
The primary structure of the DNA-binding protein II from Zymomonas mobilis has been determined from data provided by automated Edman degradation of the intact protein and of peptides derived from cleavage at aspartic acid and arginine residues. When compared with the homologous protein isolated from other bacteria, the DNA-binding protein II from Z mobilis shows many substitutions. Several non-conservative...
In the last decade, numerous polypeptide toxins acting on ion channels have been isolated and characterized from diverse scorpion venoms. These toxins are useful pharmacological probes to study ion-specific channel proteins because they interact selectively with these channels and modulate their activities. Since low amounts of natural toxins can be isolated from scorpion venoms, the chemical synthesis...
In adult humans, after milk or yogurt ingestion, many peptides derived from α sl -, β- or κ-caseins were detected in stomach, including the κ-caseinoglycopeptide, an inhibitor of platelet aggregation. Smaller peptides derived from casein and lactoferrin were recovered from duodenum. Two long peptides, the κ-caseinoglycopeptide and the N-terminal peptide of α sl -casein,...
Human red blood cells (RBCs) have a life-span of 120 days in circulation, after which they are phagocytized by resident macrophages. Extensive studies have been undertaken by many investigators in order to elucidate the cellular and molecular mechanisms of the erythrophagocytosis. The critical questions addressed by physiologists, clinicians and biochemists are: which of the many traumatic blemishes...
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