Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17931 (galectin-3)
 2,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ricin B chain is an N-glycosylated galactose-specific lectin. Examination of the amino acid sequence of the protein has shown it to be the product of a series of gene duplication events based on an original galactose binding peptide. The X-ray crystallographic structure of the protein reveals that it consists of two globular domains, each composed of three smaller subdomains. In each globular domain only one of the three subdomains has retained its ability to bind galactose. Through DNA manipulation we have created a series of fusions of portions of ricin B chain, each carrying only one galactose binding site, to the ricin signal sequence. Transcripts synthesized in vitro using SP6 RNA polymerase were injected into Xenopus oocytes where the recombinant proteins were produced in a mature form. The products were shown to be N-glycosylated and produced in a soluble stable form. Also, they retained the ability to bind galactose. Preliminary experiments on the reassociation of these ricin B chain fragments with ricin A chain to create a modified holotoxin were also carried out.
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PMID:Recombinant ricin B chain fragments containing a single galactose binding site retain lectin activity. 155 Mar 53

Ricin B chain (RTB) is an N-glycosylated galactose-specific lectin which folds into two globular domains. Each domain binds one galactoside. The x-ray crystallographic structure has shown that the two binding sites are structurally similar and contain key binding residues which hydrogen bond to the sugar, and a conserved tripeptide, Asp-Val-Arg. We have used oligonucleotide site-directed mutagenesis to change either the binding residues or the homologous tripeptide in one or other or in both of the sites. The 5' signal sequence and RTB coding region were excised from preproricin cDNA and fused in frame to generate preRTB cDNA. Transcripts synthesized in vitro from wild-type or mutant preRTB cloned into the Xenopus transcription vector pSP64T using SP6 RNA polymerase, were microinjected into Xenopus oocytes. The recombinant products were segregated into the oocyte rough endoplasmic reticulum and core-glycosylated, and the N-terminal signal peptide was removed. Mutating sugar binding sites individually did not abrogate the lectin activity of RTB. When both sites were changed simultaneously, RTB was produced which was soluble and stable but no longer able to bind galactose. Changing the Asn residues of the two RTB N-glycosylation sites to Gln showed that oligosaccharide side chains were essential for both the stability and biological activity of recombinant RTB.
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PMID:Mutational analysis of the galactose binding ability of recombinant ricin B chain. 171 62