Structural analysis of free and enzyme-bound amaranth α-amylase inhibitor: classification within the knottin fold superfamily and analysis of its functional flexibility

Oliviero Carugo, Shanyun Lu, Jingchu Luo, Xiaocheng Gu, Songping Liang, Stefan Strobl, Sándor Pongor
2001 Protein Engineering Design & Selection  
The three-dimensional structure of the amaranth α-amylase inhibitor (AAI) adopts a knottin fold of abcabc topology. Upon binding to α-amylase, it adopts a more compact conformation characterized by an increased number of intramolecular hydrogen bonds, a decreased volume and in addition a trans to cis isomerization of Pro20. A systematic analysis of the 3-D structural databanks revealed that similar proteins and domains share with AAI the characteristic presence of proline residues, many of
more » ... idues, many of which are in a cis backbone conformation. As these proteins fulfil a variety of functional roles and are expressed in very different organisms, we conclude that the structure of the knottin fold, including the propensity of the cis bond, are the result of convergent evolution.
doi:10.1093/protein/14.9.639 pmid:11707609 fatcat:tdzihe4cmbhrnmu2ok4hxck5ee