Abstract

Trigger factor (TF) is the first chaperone to interact with nascent chains and facilitate their folding within bacteria. TF possesses a three-state equilibrium in vivo: monomeric TF bound to ribosome, free monomeric, and dimeric TF in cytoplasm. TF consists of an N-terminal ribosome binding domain, a middle peptidyl–prolyl cis/trans isomerase (PPIase) domain and a C-terminal domain involved in substrate binding and dimerization. Investigation of the effect of C-terminal 13 region on TF structure and function will help to further the understanding of its mechanism as a chaperone in vitro and in vivo. Here we present TF419, a TF mutant from which the C-terminal 13 residues were deleted to investigate the role of these residues in the structure stability and function of intact molecules. Small angle X-ray scattering (SAXS), fluorescence measurements and limited proteolysis results suggested that TF transitioned to a compact conformation when the Cterminal 13 residues were truncated. Further biochemical results reveal that TF dimerization was decreased as a result of the truncation. These results suggested that the C-terminal 13 residues play an important role in structural stability and chaperone function of TF.

Keywords: C-terminal truncation, dimerization, molecular chaperone, small angle X-ray scattering, trigger factor.