A mutation in the gene of a glycolipid-binding protein (GM2 activator) that causes GM2-gangliosidosis variant AB.

GM2-gangliosidoses are neurological disorders caused by a genetic deficiency of either the beta-hexosaminidase A or the GM2 activator, a glycolipid binding protein. In a patient with an immunologically proven GM2 activator protein deficiency, A T412----C transition (counted from A of the initiation codon) was found in the coding sequence, which results in the substitution of Arg for the normal Cys107 in the mature GM2 activator protein. The remainder of the coding sequence remained entirely normal.