Draft:Balon (protein)

Balon
A rendering of Msmeg1130 (Balon analogue) in a complex with the Mycobacterium smegmatis ribosome. Balon in tan in the center.
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Msmeg1130 rotating structure

Balon is a hibernation factor protein found in the cold-adapted bacterium Psychrobacter urativorans. "Balon" means "ball" in Spanish. The name was chosen to match Pelota, a possible distant homologue whose name is also a Spanish word for "ball." Balon binds to the ribosome in order to halt the production of proteins, which can account for more than 50% of a cell's energy usage, when the cell enters a dormant state. Unlike previously discovered hibernation factors, Balon can bind to the ribosome while protein production is in process. This is important for rapid response to stress because in some cells, protein production can take up to 20 minutes to complete. Balon does this by rather than physically blocking the A site of the ribosome, as other hibernation factors do, binding near to but not across the channel, allowing it to attach to the ribosome independent of whether protein production is taking place. Balon was discovered accidentally by a researcher who unintentionally left a sample of P. urativorans in an ice bucket for too long, cold-shocking it, through subsequent cryo-EM scans of the organism's ribosomes.

Relatives of Balon have been found to also bind to the ribosome's A-site in Mycobacterium tuberculosis, which causes tuberculosis, and Thermus thermophilus, which lives in thermal vents, suggesting that it has similarly acting homologues in other species. Genetic relatives of Balon have been found in 20% of bacterial genomes catalogued in public databases, but are absent from Escherichia coli and Staphylococcus aureus, the most widely used models for cellular dormancy.