Associates with the EF-Tu.GDP complex and induces the exchange of GDP to GTP. It remains bound to the aminoacyl-tRNA.EF-Tu.GTP complex up to the GTP hydrolysis stage on the ribosome. Up-regulated more than 4 fold in the large cell variant (LCV) stage compared to the small cell variant (SCV) stage; at protein level. LCVs are thought to be more metabolically active than SCVs. Belongs to the EF-Ts family.