SLU Researcher Discovers How Hibernating Ribosomes Wake Up
In research published in Proceedings of the National Academy of Sciences (PNAS), Mee-Ngan F. Yap, Ph.D., assistant professor of biochemistry and molecular biology
at Saint Louis University, has uncovered the way a bacterial ribosome moves from an
inactive to an active form, and how that “wake up call” is key to its survival.
Often described as a cell’s protein factory, ribosomes translate messenger RNA and
link amino acids together to form new proteins. Ribosomes catalyze proteins that are
essential for all life.
In bacteria, ribosomes can take an inactive form called hibernating 100S ribosome.
Because protein synthesis accounts for more than half of a cell’s energy costs, the
inactive ribosome form helps bacteria survive under stressful conditions. During limited
nutrient access, antibiotic stress, host colonization, adaptation to the dark and
biofilm formation, bacteria aim to conserve energy by shutting down the protein factory.
Scientists have observed that the hibernating form of the ribosome is not a permanent
state and that if conditions are favorable, it can “wake up” and return to its active
form, called 70S, and begin to initiate new cycles of protein synthesis.
“The 100S form is not held together forever,” Yap said. “However, until now, the
disassociation of 100S ribosome has been a complete black box. We haven’t known how
ribosomes move from one form to the other.”
Yap was looking for the protein factor that caused the 100S form to return to the
intermediate 30S and 50S forms and subsequently into the active 70S form. Studying
Staphylococcus aureus, commonly known as staph, Yap found that a GTP hydrolase enzyme called HflX is the
wake-up call that will re-activate the ribosome.
“HflX is one way to break up the 100S ribosome structure so that it can return to
the active 70S form,” Yap said.
HflX GTPases are a family of enzymes that are evolutionarily conserved proteins, meaning
they also exist in plants, humans and other bacteria. Yap is intrigued by this finding,
because while there has been virtually no study of the protein in human cells, it
appears in genetic sequencing mapped to cancer patients and those with neurological
symptoms, including tic disorder-like syndromes. Scientists do not yet know what this
Thanks to a new five-year $1.59 million grant from the National Institutes of Health,
Yap will continue to explore these questions and others that surround hibernating
ribosomes’ role in cell survival.
Arnab Basu, Ph.D., a Saint Louis University postdoctoral fellow, is the first author
of this study.
This research was funded by the PEW Charitable Trusts, the Edward Mallinckrodt Jr.
Foundation and National Institutes of Health grant R01GM121359. The study's citation
information is: Basu A., and Yap M.-N. (2017) Disassembly of the Staphylococcus aureus hibernating 100S ribosome by an evolutionarily conserved GTPase. PNAS. doi: 10.1073/pnas.1709588114.
Saint Louis University School of Medicine
Established in 1836, Saint Louis University School of Medicine has the distinction
of awarding the first medical degree west of the Mississippi River. The school educates
physicians and biomedical scientists, conducts medical research, and provides health
care on a local, national and international level. Research at the school seeks new
cures and treatments in five key areas: cancer, liver disease, heart/lung disease,
aging and brain disease, and infectious diseases.