Figure 3.

Determining the nature of the R410W mutation. (A) At 37°C, reconstitution of Prf1^−/− CTLs with R410W mutant PRF leads to cytolytic activity (assessed by ⁵¹Cr release assays) <5% of Prf1^−/− CTLs reconstituted with wild-type perforin. (B) At 30°C (a permissive temperature for protein folding),¹¹ Prf1^−/− CTLs transfected with R410W mutant PRF have cytolytic activity that is indistinguishable from Prf1^−/− CTLs transfected with wild-type PRF. A complete recovery of R410W activity indicates that the only reason for its marginal activity at 37°C is a severe misfolding, and the mutation itself does not affect PRF function.