The native recombinant CrSGD is an autonomously formed supramolecular multimerised complex with a highly stable β-glucosidase activity. CrSGD was expressed as a recombinant protein in E. coli and total E. coli protein extracts were analysed by SDS-PAGE (a) or native PAGE (b-d) followed by Coomassie blue staining (a,c) or by β-glucosidase zymogram (b,d) without (a-b) or with (c-d) proteinase K (PK) treatments. The E. coli protein extracts from cells transformed with CrSGD-over expressing vector (S) or from control cells transformed with an empty vector (C) were boiled before electrophoresis (B) or native (N). Band annotations: 1, denatured CrSGD present as a monomer; 2, multimerised CrSGD that hardly entered the resolving gel; 3, supramolecular CrSGD that barely enter the stacking gel. Note that the multimerised and supramolecular CrSGD forms (2 and 3) present a specific β-glucosidase activity that is highly stable following PK treatments.