CYFIP1 are cytoplasmic proteins belonging to the CYFIP family. Both proteins bind GTP-bound Rac 1 to release FRM1 in its active state, which is thought to regulate mRNA translation of neural cytoskeletal proteins. A loss of CYFIP1 and CYFIP2 leads to mutant neurons with defective axonal growth and motor function. Also designated specifically Rac1-associated protein 1 (sra-1) or p140sra-1, CYFIP1 contains 1,253 amino acids and is a component of the WAVE2 complex. CYFIP1 is encoded by a gene that maps to human chromosome 15q11.2 and exists as three alternatively spliced isoforms. CYFIP2, also known as p53-inducible protein 121, contains 1,278 amino acids and plays a role in p53-dependent apoptosis. Existing as two alternatively spliced isoforms, CYFIP2 is a component of the WAVE1 complex and is encoded by a gene located on human chromosome 5q33.3.