Fragile X syndrome (FXS), the most common form of inherited mental retardation, is caused by a lack of fragile X mental retardation protein (FMRP), which regulates protein translation in the brain. Lack of FMRP leads to defects in protein translation, but until now, the mechanism underlying this relationship was not known. Simpson Joseph (University of California San Diego) and Rajendra Agrawal (State University of New York at Albany) recently showed that FMRP binds directly to the ribosome between two subunits, blocking translation factors from binding to the ribosome and thereby inhibiting protein translation (Mol. Cell doi:10.1016/j.molcel.2014.03.023; published online 8 May 2014).Lab Anim. (NY) 43, 181 (2014).