Abstract: Objective To investigate the function of general chaperones in the secretion of two-partner-secretion (TPS) protein across the inner membrane to the periplasm of Gram-negative bacteria. Methods The general chaperones were knocked-out and the strains were used to prepare spheroplast to see the effects on the secretion of FhaB^*, which is a substrate of the representative model TPS substrates FhaB/FhaC system. Results Single knock-out of chaperones Skp,DegP,PpiD,YfgM and double knock-out of PpiD/YfgM has no or little effect on the secretion of FhaB^* into the periplasm, while single knock-out of SurA or double knock-out of Skp/DegP severely affect the secretion of FhaB^*. Conclusions There may be two molecular chaperone pathways mediated by SurA or by both SKP and DegP in Gram-negative bacteria, which can mediate the substrate protein of the two-partner-secretion system secretes into the peripheral space.

Key words: two-partner-secretion, molecular chaperone, periplasm, gene knock-out, Gram-negative bacteria