TIM barrel fold and glycan moieties in the structure of ICChI, a protein with chitinase and lysozyme activity. (February 2020)

• Record Type: Journal Article
• Authors: kumar, Sunil; kumar, Ashwani; Patel, Ashok Kumar
• Is Part Of: Phytochemistry. Volume 170(2020)
• Publication Date: 2020-02
• Subjects: Ipomoea carnea -- Convolvulaceae -- Pink morning glory -- Crystallization -- Glycosylation -- Fucosylation -- TIM barrel; Botanical chemistry -- Periodicals; Biochemistry -- Periodicals; Botany -- Periodicals; Chimie végétale -- Périodiques; 572.2
• DOI: 10.1016/j.phytochem.2019.112221
• Languages: English
• ISSNs: 0031-9422

Abstract

Abstract: The ICChI is a 35-kDa, glycosylated protein isolated from the latex of the weed Ipomoea carnea . It displays chitinase and lysozyme activity, which could be important for the defense against pathogenic fungi, insects and bacteria. The ICChI enzyme was crystallized, and a diffraction data set was collected from a single crystal to 1.42 Å resolution. The crystals belong to the primitive tetragonal space group P43 21 2, with unit-cell parameters a = b = 57.9, c = 172.0 Å, and α = β = γ = 90°. The structure was elucidated by molecular replacement method using a mixed model of three homologous structures from the N-terminal sequence of ICChI. The refined model consists of 272 amino acid residues and has a Rfactor of 18.93% and Rfree of 22.42%. The protein consists of a single globular domain with a (α/β)8 triosephosphate isomerase barrel fold. Three of the consensus sites for N-glycosylation viz., Asn 45, Asn 172, and Asn 194 containing carbohydrate moieties N-Acetylglucosamine (NAG), mannose, fucose, and xylose. The putative catalytic residues are Asp 125, Glu 127, and Tyr 184 . The crystal structure may provide fundamental information of GH18 family chitinases. Graphical abstract: Image 1061 Highlights: ICChI from plant Ipomoea carnea is an enzyme with chitinase and lysozyme activity. ICChI was crystallized and diffraction data set was collected to 1.42 Å resolution. Three consensus sites for N-glycosylation, Asn 45, Asn 172 and Asn 194 were observed. The structure revealed a four-fold symmetry identical to TIM-barrel fold.