Fig. 4.

Reducing SDS/PAGE of trypsin-digested GU10-060 HA2-47G HA0 to HA1 and HA2 subdomains at different pHs. Lanes 1, 2, and 3 show GU10-060 HA0 trypsin-digested after exposure to pH 4.0, 4.9, and 8.0, respectively, which cleaves HA0 only to HA1 and HA2 (note: HA2 has different glycan forms). Trypsin did not degrade the HA exposed to low pH, as observed in other HA subtypes. Lane 4 shows uncleaved H17 HA2-47G HA0. These results suggest that GU10-060 HA requires processing to the HA1/HA2 subunits to generate the putative fusion peptide, but low-pH–induced conformational changes, which render HA susceptible to extensive degradation, are not apparent.