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. 1998 Mar 17;95(6):2828–2833. doi: 10.1073/pnas.95.6.2828

Figure 3.

Figure 3

The HIV protease specifically reduces the steady-state levels of cI.HIV. (A) The β-gal–HIV protease fusion contains amino acids 444–605 of HIV-1 GAG-POL polyprotein (31) fused in-frame to the amino-terminal 38 aa of β-gal. Autocatalytic cleavage at sites 5 and 6 releases the mature viral protease (28, 29). The control contains the identical sequences inserted in the noncoding orientation (HIVinv). (B) The cI repressors were coexpressed with the HIV protease fusion under the control of the lac promoter. Expression of the protease was induced with IPTG for 3 hr, and equivalent amounts of total cell protein were blotted with anti-cI and anti-HIV protease sera. Control, HIV protease gene inserted in the antisense orientation. The steady-state levels of the HIV protease in cells which express cI.HIV was consistently higher than in cI.HIVmt cells, possibly because of the stabilization or the reduced toxicity of the protease in the presence of the appropriate target substrate.