The SlyD metallochaperone targets iron-sulfur biogenesis pathways and the TCA cycle

Abstract

Control of protein folding is a conserved function in all domains of life. The ubiquitous peptidyl-prolyl cis-trans isomerases (PPIases) catalyze the cis/trans-isomerization of peptidyl-prolyl bonds, often a rate-limiting step for protein folding. PPIases are involved in central processes in eucaryotes but their functions in bacteria are poorly understood. We applied a large-scale two-hybrid screen to identify novel targets of SlyD, a metallochaperone PPIase, from the model organism Escherichia coli, and the important gastric pathogen Helicobacter pylori. SlyD from both organisms interacts with metal-containing proteins including TCA cycle enzymes and with enzymes driving the biogenesis of iron-sulfur (Fe-S) clusters. In H. pylori, a ∆slyD mutant contains strongly diminished amounts of MisSU, its sole Fe-S biogenesis proteins as well as diminished activity of the Fe-S aconitase. E. coli and H. pylori ∆slyD mutants are less susceptible to ampicillin and gentamicin antibiotics and under microaerobic conditions to the ROS-producing molecule hypochlorite. In addition, the intracellular ATP content and proton motive force are reduced in the H. pylori ∆slyD mutant, and its gentamicin and hypochlorite susceptibility phenotypes are rescued upon restoration of MisSU expression. Measurement of malate and fumarate in the H. pylori ∆slyD mutant suggests that the two enzymes before and after fumarase in the TCA cycle are affected. We conclude that SlyD regulates the activity of TCA cycle enzymes by controlling the efficiency of their Fe-S cluster formation. This is the first report of the role of a bacterial PPIase in central metabolism and susceptibility to stress and antibiotics.