FIG. 5.

Cooperation of hTom22 and hTom20 on preprotein import. COS-7 cells were cultured in 10-cm-diameter dishes. (A) Two micrograms of pCAGGS-pOTC was cotransfected with 4 μg of pCAGGS (control), pCAGGS-hTom20, or pCAGGS-hTom22. After culture for 20 h, cells were harvested, and cell extracts (45 μg of protein) were subjected to SDS–12% PAGE and immunoblot analysis for the indicated proteins. (B) Two micrograms of pCAGGS-pOTC was cotransfected with indicated amounts of plasmids. After 16 h of culture, cells were harvested and subjected to pulse (5-min)-chase (40-min) experiments as described in Materials and Methods. The radioactive pOTC and mature OTC (mOTC) on the SDS-polyacrylamide gel were quantified by image plate analysis, and percentages of mOTC versus pOTC plus mOTC are shown. Values are represented by means ± standard deviations of three independent experiments. p and m, precursor and mature forms, respectively.