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==The structure of hemagglutinin Q226L-G228S mutant from an avian-origin H4N6 influenza virus in complex with human receptor analog LSTc==
<StructureSection load='5xld' size='340' side='right'caption='[[5xld]], [[Resolution|resolution]] 2.30&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5xld]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Influenza_A_virus_(A/duck/Czechoslovakia/1956(H4N6)) Influenza A virus (A/duck/Czechoslovakia/1956(H4N6))]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5XLD OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5XLD FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.3&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=GAL:BETA-D-GALACTOSE'>GAL</scene>, <scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene>, <scene name='pdbligand=PRD_900046:6-sialyl-N-acetyllactosamine'>PRD_900046</scene>, <scene name='pdbligand=SIA:O-SIALIC+ACID'>SIA</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=5xld FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5xld OCA], [https://pdbe.org/5xld PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5xld RCSB], [https://www.ebi.ac.uk/pdbsum/5xld PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5xld ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/HEMA_I56A1 HEMA_I56A1] Binds to sialic acid-containing receptors on the cell surface, bringing about the attachment of the virus particle to the cell. This attachment induces virion internalization of about two third of the virus particles through clathrin-dependent endocytosis and about one third through a clathrin- and caveolin-independent pathway. Plays a major role in the determination of host range restriction and virulence. Class I viral fusion protein. Responsible for penetration of the virus into the cell cytoplasm by mediating the fusion of the membrane of the endocytosed virus particle with the endosomal membrane. Low pH in endosomes induces an irreversible conformational change in HA2, releasing the fusion hydrophobic peptide. Several trimers are required to form a competent fusion pore.  Binds to sialic acid-containing receptors on the cell surface, bringing about the attachment of the virus particle to the cell. This attachment induces virion internalization either through clathrin-dependent endocytosis or through clathrin- and caveolin-independent pathway. Plays a major role in the determination of host range restriction and virulence. Class I viral fusion protein. Responsible for penetration of the virus into the cell cytoplasm by mediating the fusion of the membrane of the endocytosed virus particle with the endosomal membrane. Low pH in endosomes induces an irreversible conformational change in HA2, releasing the fusion hydrophobic peptide. Several trimers are required to form a competent fusion pore.[HAMAP-Rule:MF_04072]
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== Publication Abstract from PubMed ==
Low-pathogenicity avian influenza viruses (LPAIVs) have caused a global concern to public health since the first novel LPAIV H7N9 outbreak occurred. The receptor-binding properties of the viral hemagglutinin are one key factor for efficient transmission and infection in humans. Recent evidence shows that H4 subtype viruses have been widely circulating in domestic poultry and human asymptomatic infections might have occurred. Here, we evaluated the receptor-binding properties of two representative isolates, avian H4N6 (containing Q226 and G228) and swine H4N6 (containing L226 and S228), and found that the avian isolate preferentially binds to avian receptors, whereas the swine isolate preferentially binds to human receptors. The Q226L and G228S substitutions are pivotal for the receptor-binding switch, which resulted in similar human receptor-binding features to the pandemic H2 and H3, implying that H4 has the potential to cause human infections. This early-warning study calls for future extensive surveillance.

Avian-to-Human Receptor-Binding Adaptation by Influenza A Virus Hemagglutinin H4.,Song H, Qi J, Xiao H, Bi Y, Zhang W, Xu Y, Wang F, Shi Y, Gao GF Cell Rep. 2017 Aug 1;20(5):1201-1214. doi: 10.1016/j.celrep.2017.07.028. PMID:28768203<ref>PMID:28768203</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 5xld" style="background-color:#fffaf0;"></div>

==See Also==
*[[Hemagglutinin 3D structures|Hemagglutinin 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Large Structures]]
[[Category: Gao FG]]
[[Category: Qi J]]
[[Category: Song H]]