FIGURE 9.

Lys-520 stabilizes phosphorylation at Ser-522. A, sequence alignment of residues 518-527 of CRMP2 from different species as well as CRMP1 and CRMP4 (h, human; m, mouse; r, rat; b, bovine; c, chick). Underlined residues show the highly conserved basic amino acids. Residues enclosed in the box are the Ser-522 phosphorylation site and proline 523, which are essential for phosphorylation of Ser-522. B, wild type (WT, ♦) and K520A (▪) GST-CRMP2 were phosphorylated in vitro by Cdk5 in the presence of [γ-³²P]ATP, then incubated with different amounts of PP1 for 30 min or for different times with 500 milliunits PP1 (C). The amount of ³²P remaining in CRMP2 was measured by Cerenkov counting, and the average percentage of phosphate remaining is shown (n = 3, ^**, p = 0.0013 K520 compared with wild type). mU, milliunits.