Elucidation of the Role of Functional Amino Acid Residues of the Small Sialidase from Clostridium perfringens by Site-Directed Mutagenesis
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Reinhard G. Kleineidam
Abstract
Bacterial sialidases represent important colonization or virulence factors. The development of a rational basis for the design of antimicrobials targeted to sialidases requires the knowledge of the exact roles of their conserved amino acids. A recombinant enzyme of the small (43 kDa) sialidase of Clostridium perfringens was used as a model in our study. Several conserved amino acids, identified by alignment of known sialidase sequences, were altered by sitedirected mutagenesis. All recombinant enzymes were affinitypurified and the enzymatic characteristics were determined. Among the mutated enzymes with modifications in the environment of the 4-hydroxyl group of bound sialic acids, D54N and D54E exhibited minor changes in substrate binding. However, a reduced activity and changes in their pH curves indicate the importance of a charged group at this area. R56K, which is supposed to bind directly to sialic acids as in the homologous Salmonella typhimurium sialidase, showed a 2500-fold reduced activity. The amino acids Asp-62 and Asp-100 are probably involved in catalysis, indicated by reduced activities and altered temperature and pH curves of mutant enzymes. Exchanging Glu-230 with threonine or aspartic acid led to dramatic decreases in activity. This residue and Y 347 are supposed to be crucial for providing a suitable environment for catalysis. However, unaltered pH curves of mutant sialidases exclude their direct involvement in protonation or deprotonation events. These results indicate that the interactions with the substrates vary in different sialidases and that they might be more complex than suggested by mere static Xray structures.
Copyright © 2001 by Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- Highlight: Glycobiology
- O-Glycosylation of the Mucin Type
- Glycoproteins from Insect Cells: Sialylated or Not?
- Congenital Disorders of Glycosylation: Glycosylation Defects in Man and Biological Models for Their Study
- Mitochondrial Single-Stranded DNA-Binding Proteins: in Search for New Functions
- Do Rodent and Human Brains Have Different N-Glycosylation Patterns?
- The Liver Flukes Fasciola gigantica and Fasciola hepatica Express the Leucocyte Cluster of Differentiation Marker CD77 (Globotriaosylceramide) in Their Tegument
- Cloning and Expression of Drosophila melanogaster UDP-GlcNAc:?-3-D-Mannoside ? 1,2-N-Acetylglucosaminyltransferase I
- Pathways of Mucin O-Glycosylation in Normal and Malignant Rat Colonic Epithelial Cells Reveal a Mechanism for Cancer-Associated Sialyl-Tn Antigen Expression
- 6-O-Sulfo De-N-Acetylsialyl Lewis X as a Novel High-Affinity Ligand for Human L-Selectin: Total Synthesis and Structural Characterization
- Segregation of Gangliosides GM1 and GD3 on Cell Membranes, Isolated Membrane Rafts, and Defined Supported Lipid Monolayers
- Structural Characterization of Fucose-Containing Oligosaccharides by High-Performance Liquid Chromatography and Matrix-Assisted Laser Desorption/ Ionization Time-of-Flight Mass Spectrometry
- Anencephaly: Structural Characterization of Gangliosides in Defined Brain Regions
- Acidic Glycerol Lipids of Trichomonas vaginalis and Tritrichomonas foetus
- Stimulation of Acid Sphingomyelinase Activity by Lysosomal Lipids and Sphingolipid Activator Proteins
- Biosynthesis of N-Acetylneuraminic Acid in Cells Lacking UDP-N-Acetylglucosamine 2-Epimerase/ N-Acetylmannosamine Kinase
- Synthesis of Nucleotide-Activated Oligosaccharides by ?-Galactosidase from Bacillus circulans
- Elucidation of the Role of Functional Amino Acid Residues of the Small Sialidase from Clostridium perfringens by Site-Directed Mutagenesis
- Biosynthesis of Lipid-Linked Oligosaccharides in Yeast: the ALG3 Gene Encodes the Dol-P-Man:Man5GlcNAc2-PP-Dol Mannosyltransferase
- Intra- and Intermolecular Triplex DNA Formation in the Murine c-myb Proto-Oncogene Promoter Are Inhibited by Mithramycin
- Experimental Regulation of STAT Gene Expression Reveals an Involvement of STAT5 in Interleukin-4-Driven Cell Proliferation
