title: An insertion in loop L7 of human eosinophil-derived neurotoxin is crucial for its antiviral activity.
abstract: The human eosinophil granule ribonuclease, eosinophil-derived neurotoxin (EDN) has been shown to have antiviral activity against respiratory syncytial virus-B (RSV-B). Other closely related and more active RNases such as RNase A, onconase, and RNase k6 do not have any antiviral activity. A remarkable unique feature of EDN is a nine-residue insertion in its carboxy-terminal loop, L7 which is not present in RNase A, and differs in sequence from the corresponding loop in another eosinophil RNase, eosinophil cationic protein (ECP). ECP has a much lower antiviral activity as compared to EDN. The current study probed the role of loop L7 of EDN in its antiviral activity. Three residues in loop L7, Arg117, Pro120, and Gln122, which diverge between EDN, ECP, and RNase A, were mutated to alanine alone and in combination to generate single, double, and triple mutants. These mutants, despite having RNase activity had decreased antiviral activity towards RSV suggesting the involvement of loop L7 in the interaction of EDN with RSV. It appears that the mutations in loop L7 disrupt the interaction of protein with the viral capsid, thereby inhibiting its entry into the virions. The study demonstrates that besides the RNase activity, loop L7 is another important determinant for the antiviral activity of EDN.
authors.affiliation: Immunochemistry Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Deepa
authors.initials: D
authors.lastname: Sikriwal
authors.forename: Divya
authors.initials: D
authors.lastname: Seth
authors.forename: Shama
authors.initials: S
authors.lastname: Parveen
authors.forename: Anu
authors.initials: A
authors.lastname: Malik
authors.forename: Shobha
authors.initials: S
authors.lastname: Broor
authors.forename: Janendra K
authors.initials: JK
authors.lastname: Batra
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000998:Antiviral Agents / Q000737:chemistry / Q000494:pharmacology*; D001120:Arginine / Q000737:chemistry; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D057075:Enzyme Assays; D047150:Eosinophil Cationic Protein / Q000737:chemistry / Q000235:genetics; D047208:Eosinophil-Derived Neurotoxin / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D005973:Glutamine / Q000737:chemistry; D054884:Host-Pathogen Interactions; D006801:Humans; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000235:genetics*; D016297:Mutagenesis, Site-Directed; D011392:Proline / Q000737:chemistry; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D012136:Respiratory Syncytial Viruses / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity; D012259:Ribonuclease, Pancreatic / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D000998:Antiviral Agents; D012367:RNA, Viral; D011994:Recombinant Proteins; D005973:Glutamine; D001120:Arginine; D011392:Proline; D047208:Eosinophil-Derived Neurotoxin; D047150:Eosinophil Cationic Protein; D012259:Ribonuclease, Pancreatic