Involved in protein export. Acts as a chaperone by maintaining the newly synthesized protein in an open conformation. Functions as a peptidyl-prolyl cis-trans isomerase (By similarity). Probably changes conformation upon binding to the ribosome (maybe in particular due to interaction with L24, PubMed:16271892), exposing a hydrophobic crevice that is probably important for its chaperone activity (PubMed:16091460 and PubMed:16271892). [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Binds to the 50S ribosomal subunit via interactions with ribosomal protein L23. Also interacts with 23S rRNA and proteins L24 and L29 when complexed with the ribosome (PubMed:16091460 and PubMed:16271892). About half TF is bound to the ribosome near the polypeptide exit tunnel while the other half is free in the cytoplasm. Consists of 3 domains; the N-terminus binds the ribosome, the middle domain has PPIase activity, while the C-terminus has intrinsic chaperone activity on its own. Belongs to the FKBP-type PPIase family. Tig subfamily.