FIG. 4.

Determination of the stability of the K-bZIP wild type and the K-bZIPK158R mutant. (A) K-bZIP wild type and K-bZIPK158R were transfected into 293 cells and cells were labeled with [³⁵S]methionine and [³⁵S]cysteine for a 4-h pulse from 24 to 28 h posttransfection. Cells were chased with medium containing nonlabeled amino acids for the indicated time periods. K-bZIP proteins were immunoprecipitated with anti-K-bZIP antibody and subjected to SDS-PAGE followed by autoradiography. (B) Quantification of the labeled protein. Protein amount was quantified by PhosphorImager analysis of the dried SDS-PAGE gel with Quantity One (Bio-Rad). Black indicates the K-bZIP wild type, while gray refers to K-bZIPK158R.