Abstract
A cryo-electron microscopy reconstruction of a stressosome complex from a Gram-negative bacterium, Vibrio vulnificus, reveals variations in subunit composition and symmetry, which could serve to adjust the activation threshold in the response to low levels of oxygen and starvation. Stressosomes are stress-sensing protein complexes widely conserved among bacteria. Although a role in the regulation ...
Abstract
A cryo-electron microscopy reconstruction of a stressosome complex from a Gram-negative bacterium, Vibrio vulnificus, reveals variations in subunit composition and symmetry, which could serve to adjust the activation threshold in the response to low levels of oxygen and starvation. Stressosomes are stress-sensing protein complexes widely conserved among bacteria. Although a role in the regulation of the general stress response is well documented in Gram-positive bacteria, the activating signals are still unclear, and little is known about the physiological function of stressosomes in the Gram-negative bacteria. Here we investigated the stressosome of the Gram-negative marine pathogen Vibrio vulnificus. We demonstrate that it senses oxygen and identified its role in modulating iron-metabolism. We determined a cryo-electron microscopy structure of the VvRsbR:VvRsbS stressosome complex, the first solved from a Gram-negative bacterium. The structure points to a variation in the VvRsbR and VvRsbS stoichiometry and a symmetry breach in the oxygen sensing domain of VvRsbR, suggesting how signal-sensing elicits a stress response. The findings provide a link between ligand-dependent signaling and an output - regulation of iron metabolism - for a stressosome complex.