title: Complete structure determination of N-acetyl-D-galactosamine-binding mistletoe lectin-3 from Viscum album L. album.
abstract: The primary structure of the B chain of the N-acetyl-D-galactosamine-recognizing mistletoe lectin-3 (ML-3B) has been deduced from proteolytic digest peptides of the purified glycoprotein, their HPLC-separation and Edman degradation and confirmation of the peptide sequences by MALDI-MS. ML-3B consists of 262 amino acid residues including 10 cysteine moieties. The structure and linkage of the carbohydrate side chains, connected to two N-glycosylation sites at positions Asn(95) and Asn(135) of the lectin, were determined by a combination of glycosidase treatment and MALDI-MS of corresponding glycopeptide fragments. The sequence alignment reveals a high homology with other B chains of type-II RIPs, although there are remarkable differences in the D-galactose-specific mistletoe lectin-1B chain. The recently published primary structure of the mistletoe lectin-3A chain1 and the now available primary sequence of the 3B chain allowed the construction of a preliminary homology model of ML-3. The model demonstrates, unequivocally, that ML-3 is a member of the type-II RIP family with rigid conservation of the enzymatic active site of the A chain and an identical overall protein fold. Specific amino acid residue exchanges and the different glycosylation pattern in comparison with ML-1 are discussed and related to the properties of the two glycoproteins. The knowledge of the complete primary structure of mistletoe lectin-3 is a major contribution towards more insight into the mechanism of the biological activity of commercial mistletoe preparations.
authors.affiliation: Abteilung für Physikalische Biochemie des Physiologisch-chemischen Instituts der Universität Tübingen, Hoppe-Seyler-Str. 4, D-72076 Tübingen, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Wacker
authors.forename: Stanka
authors.initials: S
authors.lastname: Stoeva
authors.forename: Christian
authors.initials: C
authors.lastname: Betzel
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Voelter
mesh_terms: D000116:Acetylgalactosamine / Q000737:chemistry*; D000478:Alkylation; D000595:Amino Acid Sequence; D001665:Binding Sites; D002846:Chromatography, Affinity; D017124:Conserved Sequence; D003545:Cysteine; D004591:Electrophoresis, Polyacrylamide Gel; D006386:Hemagglutination Tests; D006801:Humans; D013058:Mass Spectrometry; D014784:Mistletoe; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D028321:Plant Preparations / Q000737:chemistry* / Q000302:isolation & purification*; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification*; D054788:Ribosome Inactivating Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014118:Toxins, Biological / Q000737:chemistry* / Q000302:isolation & purification*
chemical_list: D028321:Plant Preparations; D010940:Plant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological; C488864:mistletoe lectin III; D054788:Ribosome Inactivating Proteins; D003545:Cysteine; D000116:Acetylgalactosamine