second type I K homology (KH) RNA-binding domain found in a family of fragile X mental retardation protein (FMR1) and fragile X related (FXR) proteins
The FMR1/FXR family includes FMR1 (also known as FMRP) and its two homologues, fragile X related 1 (FXR1) and 2 (FXR2). They are involved in translational regulation, particularly in neuronal cells and play an important role in the regulation of glutamate-mediated neuronal activity and plasticity. Each of these three proteins can form heteromers with the others, and each can also form homomers. Lack of expression of FMR1 results in mental retardation and macroorchidism. FXR1 and FXR2 may play important roles in the function of FMR1 and in the pathogenesis of the Fragile X Mental Retardation Syndrome. Members of this family contain three K-homology (KH) RNA-binding domains. The model corresponds to the second one.