Subunit Structure of Helix pomatia A Hemagglutinin

Equilibrium centrifugation shows that the hemagglutinin has a mol. wt. of 79, 000 ± 4, 000. It contains approximately 18 moles of half cysteine, all as disulfide bonds. Unfolding agents alone (7 M guanidine.HCl) dissociate the hemagglutinin into a subunit of mol. wt. 26, 000–30, 000. Complete reduction (DTT in 7 M guanidine.HCl) gives a single component with a mol. wt. of approximately 13, 000. Partial reduction (DTT, 8 M urea or 7 M guanidine.HCl + protective haptens D‐GalNAc or D‐GNAC) cleaves 3 to 4 SS‐bonds giving a single component with a mol. wt. of 12, 500–16, 700. Tryptic digestion gives rise to 13–14 peptides, three of which contain cysteine. Partially reduced hemagglutinin contains an intact carbohydrate binding site. The data suggest that the hemagglutinin is made up of 6 identical or closely similar polypeptide chains, each containing 1 intrachain disulfide bond and 1 carbohydrate binding site. The subunits are arranged in pairs in which a single disulfide bond links the monomers together. Native hemagglutinin is formed by the interaction of non‐covalent forces between 3 dimers.