A molecular basis for the endo-beta 1,3-glucanase activity of the thaumatin-like proteins from edible fruits.
Fruit-specific thaumatin-like proteins were isolated from cherry, apple and banana, and their enzymatic and antifungal activities compared. Both the apple and cherry possess a moderate endo-beta 1,3-glucanase activity but are devoid of antifugal activity. In contrast, the banana thaumatin-like protein inhibits the in vitro hyphal growth of Verticillium albo-atrum but is virtually devoid of endo-beta 1,3-glucanase activity. Both structural and molecular modeling studies showed that all three thaumatin-like proteins possess an extended electronegatively charged cleft at their surface, which is believed to be a prerequisite for endo-beta 1,3-glucanase activity. Docking experiments showed that the positioning of linear (1,3)-beta-D-glucans in the cleft of the apple and cherry proteins allows an interaction with the glutamic acid residues that are responsible for the hydrolytic cleavage of the glucan. Due to a different positioning in the cleft of the banana thaumatin-like protein, the linear beta-glucans cannot properly interact with the catalytic glutamic acid residues and as a result the protein possesses no enzymatic activity. The possible function of the fruit-specific thaumatin-like proteins is discussed in view of the observed biological activities and structural features.
Menu-Bouaouiche
Laurence
L
Institut de Pharmacologie et Biologie Structurale, UMR-CNRS 5089, 205, route de Narbonne, 31077 Toulouse cedex 4, France.
Vriet
Christelle
C
Peumans
Willy J
WJ
Barre
Annick
A
Van Damme
Els J M
EJ
Rougé
Pierre
P
D000935:Antifungal Agents / Q000302:isolation & purification / Q000494:pharmacology; D005638:Fruit / Q000737:chemistry* / Q000378:metabolism; D004693:Glucan Endo-1,3-beta-D-Glucosidase / Q000737:chemistry* / Q000378:metabolism; D027845:Malus; D008958:Models, Molecular; D028521:Musa; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D027861:Prunus; D013329:Structure-Activity Relationship; D020172:Verticillium / Q000187:drug effects / Q000254:growth & development
D000935:Antifungal Agents; D010940:Plant Proteins; C420118:thaumatin-like protein, Musa acuminata; C003427:thaumatin protein, plant; D004693:Glucan Endo-1,3-beta-D-Glucosidase