This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Aminoacyl tRNA synthetases catalyze the attachment of amino acids to their cognate tRNAs. They establish the algorithm of the genetic code in this first reaction of protein synthesis. Surprisingly, cells can drive these housekeeping machineries into novel functions in key signal transduction pathways beyond translation. For example, upon immune activation in mast cells, mammalian lysyl-tRNA synthetase (LysRS) is phosphorylated and translocated to the nucleus. It binds to transcription factor MITF, leading to the activation of MITF-dependent gene expression. These novel functions require conformational switch to redirect the synthetases from translation to signal transduction. Not known are the particulars of such changes. Here we aim to collect crystal diffraction data of the human aaRSs at different states at SSRL.