Neurofibromatosis type 1 (NF1), or von Reckinghausen neurofibromatosis, is one of the most common autosomal dominant disorders in humans. Early linkage analysis mapped the NF1 gene to chromosome 17. The predicted NF1 transcript encodes a 2818 amino acid protein designated NF1GRP. By sequence analysis, similarity has been demonstrated within a small region of NF1GRP and members of the Ras GAP gene family. Functionally, NF1GRP was shown by biochemical analysis involving RAS-GAP hydrolysis and functional complementation in yeast to further resemble GAP protein. The NF1 protein is expressed at relatively constant levels in a broad range of cell lines and tissues including brain, lung, liver, kidney, spleen, muscle and colon.Although little is known regarding the function of NF1GRP, the homology with the catalytic domain of proteins with GTPase activity suggests that the NF1GRP may also interact in vivo with Ras proteins.