title: Molecular and Structural Characterization of the Tegumental 20.6-kDa Protein in Clonorchis sinensis as a Potential Druggable Target.
abstract: The tegument, representing the membrane-bound outer surface of platyhelminth parasites, plays an important role for the regulation of the host immune response and parasite survival. A comprehensive understanding of tegumental proteins can provide drug candidates for use against helminth-associated diseases, such as clonorchiasis caused by the liver flukeClonorchis sinensis. However, little is known regarding the physicochemical properties ofC. sinensisteguments. In this study, a novel 20.6-kDa tegumental protein of theC. sinensisadult worm (CsTegu20.6) was identified and characterized by molecular and in silico methods. The complete coding sequence of 525 bp was derived from cDNA clones and encodes a protein of 175 amino acids. Homology search using BLASTX showed CsTegu20.6 identity ranging from 29% to 39% with previously-known tegumental proteins inC. sinensis. Domain analysis indicated the presence of a calcium-binding EF-hand domain containing a basic helix-loop-helix structure and a dynein light chain domain exhibiting a ferredoxin fold. We used a modified method to obtain the accurate tertiary structure of the CsTegu20.6 protein because of the unavailability of appropriate templates. The CsTegu20.6 protein sequence was split into two domains based on the disordered region, and then, the structure of each domain was modeled using I-TASSER. A final full-length structure was obtained by combining two structures and refining the whole structure. A refined CsTegu20.6 structure was used to identify a potential CsTegu20.6 inhibitor based on protein structure-compound interaction analysis. The recombinant proteins were expressed inEscherichia coliand purified by nickel-nitrilotriacetic acid affinity chromatography. InC. sinensis, CsTegu20.6 mRNAs were abundant in adult and metacercariae, but not in the egg. Immunohistochemistry revealed that CsTegu20.6 localized to the surface of the tegument in the adult fluke. Collectively, our results contribute to a better understanding of the structural and functional characteristics of CsTegu20.6 and homologs of flukes. One compound is proposed as a putative inhibitor of CsTegu20.6 to facilitate further studies for anthelmintics.
authors.affiliation: Division of Malaria and Parasitic Diseases, Centre for Immunology and Pathology, Korea National Research Institute of Health, Chungbuk 28159, Korea. hoiyui25@gmail.com.
authors.forename: Yu-Jung
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Division of Malaria and Parasitic Diseases, Centre for Immunology and Pathology, Korea National Research Institute of Health, Chungbuk 28159, Korea. wongi.yoo@gmail.com.
authors.forename: Won Gi
authors.initials: WG
authors.lastname: Yoo
authors.affiliation: Division of Malaria and Parasitic Diseases, Centre for Immunology and Pathology, Korea National Research Institute of Health, Chungbuk 28159, Korea. blackcg96@gmail.com.
authors.forename: Myoung-Ro
authors.initials: MR
authors.lastname: Lee
authors.affiliation: Department of Parasitology and Tropical Medicine, and Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju 52727, Korea. gjm9951001@hanmail.net.
authors.forename: Jung-Mi
authors.initials: JM
authors.lastname: Kang
authors.affiliation: Department of Parasitology and Tropical Medicine, and Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju 52727, Korea. bkna@gnu.ac.kr.
authors.forename: Byoung-Kuk
authors.initials: BK
authors.lastname: Na
authors.affiliation: Division of Malaria and Parasitic Diseases, Centre for Immunology and Pathology, Korea National Research Institute of Health, Chungbuk 28159, Korea. jo4u@cdc.go.kr.
authors.forename: Shin-Hyeong
authors.initials: SH
authors.lastname: Cho
authors.affiliation: Division of Malaria and Parasitic Diseases, Centre for Immunology and Pathology, Korea National Research Institute of Health, Chungbuk 28159, Korea. miyeoun@korea.kr.
authors.forename: Mi-Yeoun
authors.initials: MY
authors.lastname: Park
authors.affiliation: Division of Malaria and Parasitic Diseases, Centre for Immunology and Pathology, Korea National Research Institute of Health, Chungbuk 28159, Korea. jupapa@korea.kr.
authors.forename: Jung-Won
authors.initials: JW
authors.lastname: Ju
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000871:Anthelmintics / Q000737:chemistry* / Q000494:pharmacology; D001665:Binding Sites; D002118:Calcium; D003003:Clonorchiasis / Q000469:parasitology; D003004:Clonorchis sinensis / Q000235:genetics / Q000378:metabolism; D003198:Computer Simulation; D055808:Drug Discovery; D015801:Helminth Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D021381:Protein Transport; D015203:Reproducibility of Results; D013329:Structure-Activity Relationship
chemical_list: D000871:Anthelmintics; D015801:Helminth Proteins; D002118:Calcium
keywords: Clonorchis sinensis; I-TASSER; compound; docking; homology modelling; localization; structure; tegument; virtual screening