FIGURE 4.

The X-peptide pull-down assay of deletion mutants of UBR1 and UBR2. A, the X-peptide pull-down assay with N-terminal deleted and other related UBR1 fragments that were expressed in the CECF-based wheat germ extracts. The identification numbers for UBR1 fragments are shown to the left. Most UBR1 fragments are N-terminal His₆-tagged. The binding activity of each fragment was recorded as either positive (+) or negative (-). The autoradiography for the X-peptide pull-down assay is shown to the right. B, the X-peptide pull-down assay with UBR2 fragments expressed in the wheat germ extracts.