Alpha-amylase inhibitors selected from a combinatorial library of a cellulose binding domain scaffold

• A disulfide bridge-constrained cellulose binding domain (CBD,) derived from the cellobiohydrolase Ce17A from Trichoderma reesei has been investigated for use in scaffold engineering to obtain novel binding proteins. The gene encoding the wild-type 36 aa CBDWT domain was first inserted into a phagemid vector and shown to be functionally displayed on M13 filamentous phage as a protein III fusion protein with retained cellulose binding activity. A combinatorial library comprising 46 million variants of the CBD domain was constructed through randomization of 11 positions located at the domain surface and distributed over three separate beta -sheets of the domain. Using the enzyme porcine alpha-amylase (PPA) as target in biopannings, two CBD variants showing selective binding to the enzyme were characterized. Reduction and iodoacetamide blocking of cysteine residues in selected CBD variants resulted in a loss of binding activity, indicating a conformation dependent binding. Interestingly, further studies showed that the selected CBD variants were capable of competing with the binding of the amylase inhibitor acarbose to the enzyme. In addition, the enzyme activity could be partially inhibited by addition of soluble protein, suggesting that the selected CBD variants bind to the active site of the enzyme.

Keyword

phage display

in vitro selection

knottin

protein engineering

protein scaffold

in-vitro selection

3-dimensional solution structure

reesei cellobiohydrolase-i

bacterial receptor domain

phage-display technology

trichoderma-reesei

angstrom resolution

crystal-structure

affinity maturation

peptide libraries

Publication and Content Type

ref (subject category)

art (subject category)