Dr. Christian Kaiser
Johns Hopkins University
School of Medicine
Friday, October 2, 2020
“Dissecting co-translational folding in vitro and in vivo”
Large proteins with multiple domains constitute almost half of all proteins in extant proteomes. Assistance from molecular chaperones and co-translational folding ensure efficient folding of these multi-domain proteins in the cell, but the underlying mechanisms remain poorly understood. Using optical tweezers, we have dissected the folding of elongation factor G (EF-G), a multi-domain protein that requires chaperones for efficient folding. Energetic dependencies among domains determine whether folding occurs during translation or after synthesis is complete. Unexpectedly, co-translational folding does not proceed unidirectionally: unfolded polypeptide emerging from the ribosome can denature an already folded domain. The chaperone trigger factor protects against denaturation, thus helping multi-domain proteins overcome inherent challenges during co-translational folding – a novel role for ribosome-binding chaperones. We are complementing our single-molecule experiments with measurements in live cells. Collectively, these studies help to define principles of co-translational multi-domain protein folding.