6BBD

Structure of N-glycosylated porcine surfactant protein-D complexed with glycerol

Summary for 6BBD

• Entry DOI: 10.2210/pdb6bbd/pdb
• Related: 4DN8
• Descriptor: Pulmonary surfactant-associated protein D, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-2)-alpha-D-mannopyranose-(1-6)-beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, CALCIUM ION, ... (5 entities in total)
• Functional Keywords: innate immunity, surfactant, n-linked glycan, c-type lectin, surfactant protein
• Biological source: Sus scrofa (Pig)
• Total number of polymer chains: 1
• Total formula weight: 17997.89

Authors

van Eijk, M.,Rynkiewicz, M.J.,Khatri, K.,Leymarie, N.,Zaia, J.,White, M.R.,Hartshorn, K.L.,Cafarella, T.R.,van Die, I.,Hessing, M.,Seaton, B.A.,Haagsman, H.P. (deposition date: 2017-10-18, release date: 2018-05-23, Last modification date: 2024-10-30)

Primary citation

van Eijk, M.,Rynkiewicz, M.J.,Khatri, K.,Leymarie, N.,Zaia, J.,White, M.R.,Hartshorn, K.L.,Cafarella, T.R.,van Die, I.,Hessing, M.,Seaton, B.A.,Haagsman, H.P.
Lectin-mediated binding and sialoglycans of porcine surfactant protein D synergistically neutralize influenza A virus.
J. Biol. Chem., 293:10646-10662, 2018

PubMed Abstract: Innate immunity is critical in the early containment of influenza A virus (IAV) infection, and surfactant protein D (SP-D) plays a crucial role in the pulmonary defense against IAV. In pigs, which are important intermediate hosts during the generation of pandemic IAVs, SP-D uses its unique carbohydrate recognition domain (CRD) to interact with IAV. An -linked CRD glycosylation provides interactions with the sialic acid-binding site of IAV, and a tripeptide loop at the lectin-binding site facilitates enhanced interactions with IAV glycans. Here, to investigate both mechanisms of IAV neutralization in greater detail, we produced an -glycosylated neck-CRD fragment of porcine SP-D (RpNCRD) in HEK293 cells. X-ray crystallography disclosed that the -glycan did not alter the CRD backbone structure, including the lectin site conformation, but revealed a potential second nonlectin-binding site for glycans. IAV hemagglutination inhibition, IAV aggregation, and neutralization of IAV infection studies showed that RpNCRD, unlike the human analogue RhNCRD, exhibits potent neutralizing activity against pandemic A/Aichi/68 (H3N2), enabled by both porcine-specific structural features of its CRD. MS analysis revealed an -glycan site-occupancy of >98% at Asn-303 of RpNCRD with complex-type, heterogeneously branched and predominantly α(2,3)-sialylated oligosaccharides. Glycan-binding array data characterized both RpNCRD and RhNCRD as mannose-type lectins. RpNCRD also bound Lewis structures, whereas RhNCRD bound polylactosamine-containing glycans. The presence of the -glycan in the CRD increases the glycan-binding specificity of RpNCRD. These insights increase our understanding of porcine-specific innate defense against pandemic IAV and may inform the design of recombinant SP-D-based antiviral drugs.

PubMed: 29769321
DOI: 10.1074/jbc.RA117.001430

Experimental method

X-RAY DIFFRACTION (1.898 Å)