CtaM Is Required for Menaquinol Oxidase aa ₃ Function in Staphylococcus aureus

Abstract

Staphylococcus aureus is the leading cause of skin and soft tissue infections, bacteremia, osteomyelitis, and endocarditis in the developed world. The ability of S. aureus to cause substantial disease in distinct host environments is supported by a flexible metabolism that allows this pathogen to overcome challenges unique to each host organ. One feature of staphylococcal metabolic flexibility is a branched aerobic respiratory chain composed of multiple terminal oxidases. Whereas previous biochemical and spectroscopic studies reported the presence of three different respiratory oxygen reductases (o type, bd type, and aa3 type), the genome contains genes encoding only two respiratory oxygen reductases, cydAB and qoxABCD. Previous investigation showed that cydAB and qoxABCD are required to colonize specific host organs, the murine heart and liver, respectively. This work seeks to clarify the relationship between the genetic studies showing the unique roles of the cydAB and qoxABCD in virulence and the respiratory reductases reported in the literature. We establish that QoxABCD is an aa3-type menaquinol oxidase but that this enzyme is promiscuous in that it can assemble as a bo3-type menaquinol oxidase. However, the bo3 form of QoxABCD restricts the carbon sources that can support the growth of S. aureus. In addition, QoxABCD function is supported by a previously uncharacterized protein, which we have named CtaM, that is conserved in aerobically respiring Firmicutes. In total, these studies establish the heme A biosynthesis pathway in S. aureus, determine that QoxABCD is a type aa3 menaquinol oxidase, and reveal CtaM as a new protein required for type aa3 menaquinol oxidase function in multiple bacterial genera.

Nitrite Derived from Endogenous Bacterial Nitric Oxide Synthase Activity Promotes Aerobic Respiration

“…6F and G ). As ctaM is thought to affect integration of heme A and heme O into quinol oxidases ( 17 ), our results collectively suggest that nitrite excreted due to NOS activity directly activates respiration by affecting quinol oxidase function.…”

“…Finally, we tested if S. aureus cytochromes (quinol oxidase and CydBD encoded by the qoxABCD and cydAB operons, respectively) were the target of nitrite. Inactivation of cytochromes can result in growth defects ( 16 , 17 ). If the growth defect associated with a nos mutation resulted from its ability to modulate cytochrome activity, we would expect that qoxA nos and cydA nos double mutants would not have an additive growth defect relative to their respective single mutants.…”

“…Since quinol oxidase houses both heme A and heme O, resulting in cytochrome aa 3 and cytochrome bo , respectively, we next attempted to determine which of these cytochromes are targeted by nos- derived nitrite. Inactivation of ctaA abrogates heme A, whereas mutation of ctaB abolishes both heme O and heme A biosynthesis ( 17 ). However, relative to ctaA and ctaB single mutants, addition of nitrite rescued growth of the ctaA nos mutant ( Fig.…”

Staphylococcus aureus HemX Modulates Glutamyl-tRNA Reductase Abundance To Regulate Heme Biosynthesis

“…S. aureus , as a facultative anaerobe, generates energy through aerobic respiration, anaerobic respiration, or fermentation. The final step in aerobic respiration is reduction of oxygen to water, which S. aureus performs with either of the heme-dependent QoxABCD or CydAB terminal oxidases ( 3 , 4 ). Although a great deal is known about heme synthesis, heme utilization, and heme toxicity in S. aureus , no heme synthesis regulatory pathway has been identified in this organism.…”

Absence of Protoheme IX Farnesyltransferase CtaB Causes Virulence Attenuation but Enhances Pigment Production and Persister Survival in MRSA

“…(Drabkin, 1951 ; Mazmanian et al, 2003 ; Liu et al, 2008 ; Mason and Skaar, 2009 ). However, in an environment without heme-iron, S. aureus has to synthesize heme A with a complex pathway starting from glutamate (Hammer et al, 2016 ). CtaB and CtaA catalyzes the last two steps of the process.…”