Deciphering the protein folding function of Mycobacterial chaperonins

Abstract:

Mycobacterium tuberculosis produces two chaperonin proteins, MtbCpn60.1 and MtbCpn60.2, which share significant sequence similarity with the Escherichia coli chaperonin, GroEL. Unlike GroEL, MtbCpn60.1 and MtbCpn60.2 form lower-order oligomers. Previous studies have shown that MtbCpn60.2 can replace GroEL in E. coli, while the function of MtbCpn60.1 remained unclear. In this study, we investigate the molecular chaperone functions of MtbCpn60.1 and MtbCpn60.2 by assessing their ability to assist in the folding of specific chaperonin clients, such as DapA, FtsE, and MetK, in an E. coli strain lacking endogenous GroEL. Our results indicate that both MtbCpn60.1 and MtbCpn60.2 support cell survival and division by aiding the folding of DapA and FtsE. However, only MtbCpn60.2 fully compensates for the absence of GroEL in E. coli cells. Additionally, we find that, unlike MtbCpn60.2, MtbCpn60.1 has a limited ability to promote cell growth and assist in the folding of MetK. These findings suggest that while GroEL and MtbCpn60.2 have largely overlapping client pools, MtbCpn60.1 folds only a subset of GroEL clients. We conclude that the functional differences between MtbCpn60.1 and MtbCpn60.2 may be due to their intrinsic sequence characteristics, affecting their stability, efficiency, client range, and modes of action.