Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The carbohydrate-recognition domain of rat serum mannose-binding protein A has been subjected to random cassette mutagenesis. Mutant domains, expressed in bacteria, were initially screened for binding to invertase-coated nitrocellulose and then analyzed further for Ca2+ affinity, saccharide binding, resistance to proteolysis, and oligomerization. The results are consistent with previous evolutionary and structural studies. Six out of seven completely inactive mutants have changes in residues directly involved in ligating Ca2+. Most changes in conserved residues which form part of the hydrophobic core characteristic of Ca(2+)-dependent (C-type) animal lectins result in decreased affinity for Ca2+, even though these residues are distant from the Ca2+ sites. Changes can be made in large portions of the surface without affecting saccharide binding. The results indicate that the precise arrangement of the regular portion of the domain containing the hydrophobic core is necessary for formation of a stable Ca(2+)-ligated structure under physiological conditions. The data also suggest that the saccharide-binding site is likely to be in close proximity to the bound Ca2+.
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PMID:Role of conserved and nonconserved residues in the Ca(2+)-dependent carbohydrate-recognition domain of a rat mannose-binding protein. Analysis by random cassette mutagenesis. 158 59

Human serum contains lectins which inhibit the uptake of mannose- and N-acetylglucosamine-terminated glycoproteins by isolated rat hepatic sinusoidal cells. In these experiments, calcium-dependent and calcium-independent human serum mannose-binding proteins have been isolated by affinity chromatography using mannan linked to four different supports. In electroblots both calcium-dependent and -independent serum mannose-binding proteins bound radioiodinated mannan and invertase in the presence of calcium ions, but the binding of calcium-dependent serum mannose-binding proteins was abolished by EDTA. Chicken antibodies were raised against serum mannose-binding proteins and an ELISA was developed. The principal calcium-independent serum mannose-binding protein is mannose-specific IgG as judged by immunodiffusion and electroblotting with anti-human IgG antibodies. The calcium-dependent serum mannose-binding protein is probably the secreted form of an intracellular hepatocyte mannose-binding protein since: antibodies raised against the 30 kDa subunit of the calcium-dependent serum mannose-binding protein also bound 30 kDa subunits of whole liver homogenate and purified human liver mannose-binding protein; antibodies to the human liver mannose-binding protein bound to the 30 kDa subunit of the calcium-dependent serum mannose-binding protein; and the binding specificities of the calcium-dependent serum mannose-binding protein for N-acetylglucosamine and fucose as well as mannose, and its recognition of the core region of an oligosaccharide rather than only the peripheral sugars, were identical to those reported for the hepatocyte mannose-binding protein. The physiological ligands of these serum mannose-binding proteins are unknown but they could bind noxious glycoproteins which enter the circulation prior to their removal by the sinusoidal mannose receptor.
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PMID:Mannose-binding proteins in human serum: identification of mannose-specific immunoglobulins and a calcium-dependent lectin, of broader carbohydrate specificity, secreted by hepatocytes. 374 82