Structural basis for carbohydrate binding properties of a plant chitinase-like agglutinin with conserved catalytic machinery.
A new chitinase-like agglutinin, RobpsCRA, related to family GH18 chitinases, has previously been identified in black locust (Robinia pseudoacacia) bark. The crystal structure of RobpsCRA at 1.85Å resolution reveals unusual molecular determinants responsible for the lack of its ancestral chitinase activity. Unlike other chitinase-like proteins, which lack chitinase catalytic residues, RobpsCRA has conserved its catalytic machinery. However, concerted rearrangements of loop regions coupled to non-conservative substitutions of aromatic residues central to the chitin-binding groove explain the lack of hydrolytic activity against chitin and the switch toward recognition of high-mannose type N-glycans. Identification of close homologs in flowering plants with conservation of sequence motifs associated to the structural adaptations seen in RobpsCRA defines an emerging class of agglutinins, as emphasized by a phylogenetic analysis, that are likely to share a similar carbohydrate binding specificity for high-mannose type N-glycans. This study illustrates the recent evolution and molecular adaptation of a versatile TIM-barrel scaffold within the ancestral GH18 family.
Aix-Marseille University, AFMB UMR 7257, 13288 Marseille, France; CNRS, AFMB UMR 7257, 13288 Marseille, France.
Gerlind
G
Sulzenbacher
Aix-Marseille University, AFMB UMR 7257, 13288 Marseille, France; CNRS, AFMB UMR 7257, 13288 Marseille, France.
Véronique
V
Roig-Zamboni
Department of Molecular Biotechnology, Laboratory of Biochemistry and Glycobiology, Ghent University, Coupure links 653, B-9000 Ghent, Belgium.
Willy J
WJ
Peumans
Aix-Marseille University, AFMB UMR 7257, 13288 Marseille, France; CNRS, AFMB UMR 7257, 13288 Marseille, France.
Bernard
B
Henrissat
Department of Molecular Biotechnology, Laboratory of Biochemistry and Glycobiology, Ghent University, Coupure links 653, B-9000 Ghent, Belgium.
Els J M
EJ
van Damme
Aix-Marseille University, AFMB UMR 7257, 13288 Marseille, France; CNRS, AFMB UMR 7257, 13288 Marseille, France. Electronic address: yves.bourne@afmb.univ-mrs.fr.
Yves
Y
Bourne
D000373:Agglutinins / Q000032:analysis* / Q000737:chemistry; D002384:Catalysis; D002688:Chitinases / Q000032:analysis; D002850:Chromatography, Gel; D003460:Crystallization; D019143:Evolution, Molecular; D006868:Hydrolysis; D016013:Likelihood Functions; D008957:Models, Genetic; D008958:Models, Molecular; D010802:Phylogeny; D024301:Plant Bark / Q000737:chemistry*; D011134:Polysaccharides / Q000378:metabolism; D011487:Protein Conformation; D031301:Robinia / Q000737:chemistry*
D000373:Agglutinins; D011134:Polysaccharides; D002688:Chitinases
Chitinase-like proteins; Crystal structure; Family 18 glycoside hydrolase; High-mannose-type N-glycan; Plant lectins; TIM-barrel fold