7k37

From Proteopedia

Structure of full-length influenza HA with a head-binding antibody at pH 7.8

Structural highlights

7k37 is a 12 chain structure with sequence from Homo sapiens and Influenza A virus (A/Hong Kong/1/1968(H3N2)). Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	Electron Microscopy, Resolution 2.8Å
Ligands:	, ,
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

HEMA_I68A4 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 (By similarity).

Publication Abstract from PubMed

The hemagglutinin (HA) glycoproteins of influenza viruses play a key role in binding host cell receptors and in mediating virus-host cell membrane fusion during virus infection. Upon virus entry, HA is triggered by low pH and undergoes large structural rearrangements from a prefusion state to a postfusion state. While structures of prefusion state and postfusion state of HA have been reported, the intermediate structures remain elusive. Here, we report two distinct low pH intermediate conformations of the influenza virus HA using cryo-electron microscopy (cryo-EM). Our results show that a decrease in pH from 7.8 to 5.2 triggers the release of fusion peptides from the binding pockets and then causes a dramatic conformational change in the central helices, in which the membrane-proximal ends of the central helices unwind to an extended form. Accompanying the conformational changes of the central helices, the stem region of the HA undergoes an anticlockwise rotation of 9.5 degrees and a shift of 15 A. The HA head, after being stabilized by an antibody, remains unchanged compared to the neutral pH state. Thus, the conformational change of the HA stem region observed in our research is likely to be independent of the HA head. These results provide new insights into the structural transition of HA during virus entry.

Structural intermediates in the low pH-induced transition of influenza hemagglutinin.,Gao J, Gui M, Xiang Y PLoS Pathog. 2020 Nov 30;16(11):e1009062. doi: 10.1371/journal.ppat.1009062. , eCollection 2020 Nov. PMID:33253316^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Gao J, Gui M, Xiang Y. Structural intermediates in the low pH-induced transition of influenza hemagglutinin. PLoS Pathog. 2020 Nov 30;16(11):e1009062. PMID:33253316 doi:10.1371/journal.ppat.1009062