Regions with NMR signals that are affected by Rac1 binding are boxed and shaded in the secondary structure strip (top), and the locations of the two PRAM segmentsare indicated. X denotes any amino acid, [ABC] denotes either A, B, or C; a indicates aliphatic residues [AILMV], and + positively charged residues [HKR]. Residues that are invariant across all the plexins aligned here have a yellow background, highly conserved residues have a blue background, and chemically similar residues a green background.