A new lectin family with structure similarity to actinoporins revealed by the crystal structure of Xerocomus chrysenteron lectin XCL.
A newly defined family of fungal lectins displays no significant sequence similarity to any protein in the databases. These proteins, made of about 140 amino acid residues, have sequence identities ranging from 38% to 65% and share binding specificity to N-acetyl galactosamine. One member of this family, the lectin XCL from Xerocomus chrysenteron, induces drastic changes in the actin cytoskeleton after sugar binding at the cell surface and internalization, and has potent insecticidal activity. The crystal structure of XCL to 1.4 A resolution reveals the architecture of this new lectin family. The fold of the protein is not related to any of the several lectin folds documented so far. Unexpectedly, the structure similarity is significant with actinoporins, a family of pore-forming toxins. The specific structural features and sequence signatures in each protein family suggest a potential sugar binding site in XCL and a possible evolutionary relationship between these proteins. Finally, the tetrameric assembly of XCL reveals a complex network of protomer-protomer interfaces and generates a large, hydrated cavity of 1000 A3, which may become accessible to larger solutes after a small conformational change of the protein.
Birck
Catherine
C
Département de Génomique et Biologie Structurales, IGBMC CNRS/INSERM/ULP, 1 rue Laurent Fries, BP 10142, 67404-Illkirch CU Strasbourg, France.
Damian
Luminita
L
Marty-Detraves
Claire
C
Lougarre
Andrée
A
Schulze-Briese
Clemens
C
Koehl
Patrice
P
Fournier
Didier
D
Paquereau
Laurent
L
Samama
Jean-Pierre
JP
D000595:Amino Acid Sequence; D001487:Basidiomycota / Q000737:chemistry*; D001665:Binding Sites; D050260:Carbohydrate Metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D037102:Lectins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D016415:Sequence Alignment; D013379:Substrate Specificity
D037102:Lectins