Table 3.
D-box and NLS/NES motifs of the Id proteins
| Id motif | Amino-acid sequence |
|---|---|
| D-box | |
| Id1 (126–133) | RAPLSTLN |
| Id2 (100–107) | RTPLTTLN |
| Id4 (137–144) | RTPLTALN |
| NES-like | |
| Id1 (98–109) | VIDYIRDLQLEL |
| Id2 (106–115) | LNTDISILSL |
| NLS-like | |
| Id1 (74–91) | SRLKELVPTLPQNRKVSK |
| Id2 (44–61) | SKLKELVPSIPQNKKVSK |
The D-box motifs are recognized by Apc/CCdh1 and trigger Id-protein degradation. The characteristic D-box amino-acid positions are in bold [50]. The NLS/NES motifs regulate the Id-protein nucleo-cytoplasmic shuttling [51, 126, 129]. The hydrophobic residues important for the nuclear export are in bold. The conserved basic positions in the NLS motifs are in bold