A novel artificial cellulase was developed by conjugating a DNA aptamer to an endoglucanase catalytic domain, thereby substituting the natural carbohydrate-binding module. Circular dichroism spectroscopy and adsorption isotherm showed the binding motif of cellulose-binding DNA aptamer (CelApt) was G-quadruplex and stem-loop structures stabilized in the presence of salts, and CelApt binding preferred the amorphous region of the solid cellulose. By introducing the revealed salt-switchable cellulose-binding nature of CelApt into a catalytic domain of a cellulase, we created CelApt-catalytic domain conjugate possessing both controllable adsorption on the solid substrates and equal enzymatic activity to the wild-type cellulase. Thus potential use of a responsive DNA aptamer for biocatalysis at a solid surface was demonstrated.
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