Crystal structure of the noncompetitive xylanase inhibitor TLXI, member of the small thaumatin-like protein family

The crystal structure of the thaumatin-like xylanase inhibitor (TLXI) from Triticum aestivum, a non-competitive inhibitor of glycoside hydrolase family 11 xylanases, has been determined at 2.9 Å resolution. It is similar to that of thaumatin except that TLXI lacks domain II of thaumatin, making it the first obtained crystallographic structure in the small thaumatin-like proteins (TLPs) subfamily within the larger family of TLPs. Unlike most other TLPs, TLXI does not contain the acidic surface cleft which is responsible for antifungal activity and binding of carbohydrates. Comparison with other TLPs suggests the loop containing histidine 22 as being important for xylanase inhibition.