Structural Analysis of the Laetiporus sulphureus Hemolytic Pore-forming Lectin in Complex with Sugars

• Published in: The Journal of biological chemistry 2005-04, Vol.280 (17), p.17251-17259
• Main Authors: Mancheño, José M., Tateno, Hiroaki, Goldstein, Irwin J., Martínez-Ripoll, Martín, Hermoso, Juan A.
• Format: Article
• Language: English
• Subjects: Abrin - chemistry; Aeromonas hydrophila - metabolism; Agaricales - metabolism; Amino Acid Motifs; Amino Acid Sequence; Amino Sugars - chemistry; Binding Sites; Carbohydrates - chemistry; Clostridium botulinum - metabolism; Clostridium perfringens - metabolism; Crystallography, X-Ray; Disaccharides - chemistry; Galactose - chemistry; Lactose - chemistry; Lectins - chemistry; Models, Molecular; Molecular Sequence Data; Platinum - chemistry; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Ricin - chemistry; Sequence Homology, Amino Acid; Ultracentrifugation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M413933200

LSL is a lectin produced by the parasitic mushroom Laetiporus sulphureus, which exhibits hemolytic and hemagglutinating activities. Here, we report the crystal structure of LSL refined to 2.6-Å resolution determined by the single isomorphous replacement method with the anomalous scatter (SIRAS) signal of a platinum derivative. The structure reveals that LSL is hexameric, which was also shown by analytical ultracentrifugation. The monomeric protein (35 kDa) consists of two distinct modules: an N-terminal lectin module and a pore-forming module. The lectin module has a β-trefoil scaffold that bears structural similarities to those present in toxins known to interact with galactose-related carbohydrates such as the hemagglutinin component (HA1) of the progenitor toxin from Clostridium botulinum, abrin, and ricin. On the other hand, the C-terminal pore-forming module (composed of domains 2 and 3) exhibits three-dimensional structural resemblances with domains 3 and 4 of the β-pore-forming toxin aerolysin from the Gram-negative bacterium Aeromonas hydrophila, and domains 2 and 3 from the ϵ-toxin from Clostridium perfringens. This finding reveals the existence of common structural elements within the aerolysin-like family of toxins that could be directly involved in membrane-pore formation. The crystal structures of the complexes of LSL with lactose and N-acetyllactosamine reveal two dissacharide-binding sites per subunit and permits the identification of critical residues involved in sugar binding.