X-ray crystallographic determination of the structure of the influenza C virus haemagglutinin-esterase-fusion glycoprotein.
The structure of the haemagglutinin-esterase-fusion (HEF) glycoprotein from influenza C virus has been determined to 3.2 A resolution by X-ray crystallography. A synthetic mercury-containing esterase inhibitor and receptor analogue, 9-acetamidosialic acid alpha-thiomethylmercuryglycoside, was designed as the single isomorphous heavy-atom derivative. The asymmetric unit of one crystal form (form I; P4322, a = b = 155.4, c = 414.4 A) contained an HEF trimer. Six mercury sites identifying the three haemagglutination and three esterase sites were located by difference Patterson map analysis of a 6.5 A resolution derivative data set. These positions defined the molecular threefold-symmetry axis of the HEF trimer. A molecular envelope was defined by averaging a 7.0 A resolution electron-density map, phased by single isomorphous replacement (SIR), about the non-crystallographic threefold-symmetry axis. Iterative non-crystallographic symmetry averaging in real space, solvent flattening and histogram matching were used to extend the phases to 3.5 A resolution. Molecular replacement of the model into a second crystal form (form II; P43212, a = b = 217.4, c = 421.4 A) containing two HEF trimers per asymmetric unit permitted iterative ninefold averaging of the electron density. The 3.5 A electron-density map allowed an unambiguous tracing of the polypeptide chain and identification of N-linked carbohydrates. The model has been refined by least squares to 3.2 A resolution (Rfree = 26.7%).
Zhang
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X
Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Rosenthal
P B
PB
Formanowski
F
F
Fitz
W
W
Wong
C H
CH
Meier-Ewert
H
H
Skehel
J J
JJ
Wiley
D C
DC
D000115:Acetylesterase / Q000737:chemistry*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006023:Glycoproteins / Q000737:chemistry*; D006389:Hemagglutinins, Viral / Q000737:chemistry*; D009982:Gammainfluenzavirus / Q000201:enzymology*; D008628:Mercury / Q000737:chemistry; D008958:Models, Molecular; D011487:Protein Conformation; D014760:Viral Fusion Proteins / Q000737:chemistry*
D006023:Glycoproteins; D006389:Hemagglutinins, Viral; D014760:Viral Fusion Proteins; C060814:hemagglutinin esterase; D000115:Acetylesterase; D008628:Mercury