title: The extended loop of the C-terminal carbohydrate-recognition domain of Manduca sexta immulectin-2 is important for ligand binding and functions.
abstract: Our previous research showed that immulectin-2 (IML-2), a C-type lectin from the tobacco hornworn, Manduca sexta, is a pattern recognition receptor (PRR) that can bind to pathogen-associated molecular patterns (PAMPs), such as lipopolysaccharide (LPS), peptidoglycan (PG) and β-1,3-glucan, and IML-2 plays an important role in cellular encapsulation, melanization, phagocytosis, and prophenoloxidase (proPO) activation. Unlike most mammalian C-type lectins that contain a single carbohydrate-recognition domain (CRD), IML-2 is composed of tandem CRDs, and the C-terminal CRD2 contains an extended loop, which is not present in most C-type CRDs. We hypothesize that the extended loop may participate in ligand binding, encapsulation, melanization, phagocytosis and/or proPO activation in M. sexta. To test this hypothesis, two deletion mutant proteins (IML-2Δ220-244 and IML-2Δ220-257), in which the extended loop of the CRD2 was partially or completely deleted, were expressed and purified. By comparing the characteristics of recombinant IML-2, IML-2Δ220-244 and IML-2Δ220-257, we found that deletion of the extended loop in CRD2 impaired the ability of IML-2 to bind microbial PAMPs and to stimulate proPO activation, indicating that the extended loop of IML-2 plays an important role in ligand binding and biological functions.
authors.affiliation: Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, 5007 Rockhill Road, Kansas City, MO 64110, USA.
authors.forename: Xiu-Zhen
authors.initials: XZ
authors.lastname: Shi
authors.forename: Xiao-Qiang
authors.initials: XQ
authors.lastname: Yu
mesh_terms: D000818:Animals; D001412:Bacillus subtilis / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D006434:Hemocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D006458:Hemolymph / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D007814:Larva / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D037181:Lectins, C-Type / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D008024:Ligands; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D018402:Manduca / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D050505:Mutant Proteins / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D010587:Phagocytosis / Q000276:immunology; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D013211:Staphylococcus aureus / Q000737:chemistry
chemical_list: D019476:Insect Proteins; D037181:Lectins, C-Type; D008024:Ligands; D008070:Lipopolysaccharides; D050505:Mutant Proteins; D011994:Recombinant Proteins; C417733:immulectin-2 protein, Manduca sexta