an unknown function domain of Listeria innocua LinChi78 GH18 chitinase that is essential for its catalytic activity; found in similar chitinase-like proteins
This domain is referred to as an unknown-function region (UFR) and shown to be necessary for the hydrolytic activity of LinChi78 glycosyl hydrolase family 18 (GH18) chitinase (a product of the lin0153gene) from the nonpathogenic bacterium Listeria innocua. The catalytic domain (CatD) of GH18 chitinases folds into a TIM barrel and has a conserved DXXDXDXE motif, in which the Glu residue functions as a catalytic residue; these chitinases contain additional domains such as a chitin-binding domain (ChBD) and/or a fibronectin type III-like (FnIII) domain. LinChi78 consists of a CatD, a FnIII, and a ChBD domain, and has this UFR region located between the CatD and the FnIII domain. Its catalytic site is composed of a typical CatD and a portion of this UFR, in particular the key Gln and Ile residues which are indispensable for LinChi78 to exhibit full catalytic activity. This UFR domain is also found in proteins where it is located between a CatD domain and DUF5011 and ChBD(s) domains. LinChi78 exhibits chitinase activity towards artificial and natural substrates, including colloidal chitin and chitin oligosaccharides of various lengths, and hydrolyzes these in a processive manner. Members of this family include some uncharacterized chitinase-like proteins from pathogenic bacteria such as Listeria monocytogenes and Clostridium botulinum.
Comment:amino acid residues essential for chitinase activity
Comment:LinChi78 has a unique catalytic region composed of a typical catalytic domain and a portion of the UFR, particularly the highlighted Gln and Ile, which are indispensable for construction of the LinChi78 active site for the enzyme to exhibit full catalytic activity
Jiyao W et al.(2023). "The conserved domain database in 2023.",