FIGURE 7.

Proteinase K sensitivity of cleaved and uncleaved JRFL trimers. A, SEC-purified trimers from 293F or GnTI⁻ cells were treated with Proteinase K at the indicated concentrations for 1 h at 37 °C and electrophoresed on a reducing SDS gel followed by Coomassie Blue staining. The 37 °C lane corresponds to control sample incubated at 37 °C for 1 h without Proteinase K. Note that the uncleaved trimers are more susceptible to proteolysis than the cleaved trimers and also that the 293F trimers are more susceptible to proteolysis than the GnTI⁻ trimers. B, densitometric quantification of the undigested gp140 bands from A.