EF-Ts (elongation factor thermo stable) is one of the prokaryotic elongation factors. It is found in human mitochrondria as TSFM. It is similar to eukaryotic EF-1B. EF-Ts serves as the guanine nucleotide exchange factor for EF-Tu (elongation factor thermo unstable), catalyzing the release of guanosine diphosphate from EF-Tu. This enables EF-Tu to bind to a new guanosine triphosphate molecule, release EF-Ts, and go on to catalyze another aminoacyl tRNA addition. EF-Ts functions as guanine nucleotide exchange factor, it catalyzes the reaction of EF-Tu*GDP ( inactive form) to EF-Tu*GTP (active). EF-Tu (active) then delivers the aminoacyl-tRNA to the ribosome. Therefore, EF-Ts main role is recycling EF-Tu back to its active state in order to complete another elongation cycle.