Roles Of Hydrophobic Regions In The Molecular Chaperone Function Of Trigger Factor

Molecular chaperones are a functionally related group of proteins which are in-volved in numerous cellular physiological processes, including folding of nascent pep-tides, maintenance of protein conformation, protein degradation etc. These chaperonescooperate with each other and form a complex functional network, which plays an im-portant role in the maintenance of cellular protein homeostasis.Trigger factor (TF) is a key member of prokaryotic chaperone network, and par-ticipates in many important physiological processes. TF consists of three domains.While N-terminal domain and C-terminal domain build a crevice to provide a shieldspace for the folding of nascent chains, M-domain, which carries PPIase activity, canaccelerate the folding rate of proteins. As an ATP-independent chaperone, TF may im-prove the folding of nascent chains by multiple cycles of binding and release with sub-strates. Crystal structure of TF reveals that there are several hydrophobic regions on theinner surface of crevice, which are suggested to be responsible for substrate recognition.However, the exact role of each hydrophobic region is unclear yet. Here, we investigatethe role of these hydrophobic regions in chaperone function of TF using lysozyme,BCAII and GAPDH as substrate. It is found that the replacement of hydrophobic resi-dues in different hydrophobic regions has different impact on the chaperone function ofTF, indicating that TF has a complicated substrate recognition mechanism. Our resultsnot only contribute to the understanding of structure and function of TF but also arehelpful for us to rationally design novel TF variants to improve expression efficiency ofheterologous proteins.