The Peptide Methionine Sulfoxide Reductase (MsrAB) of Haemophilus influenzae Repairs Oxidatively Damaged Outer Membrane and Periplasmic Proteins Involved in Nutrient Acquisition and Virulence

Abstract

Sulfoxide-damage repair mechanisms are emerging as essential for the virulence of bacterial pathogens, and in the human respiratory pathogen Haemophilus influenzae the periplasmic MsrAB peptide methionine sulfoxide reductase is necessary for resistance to reactive chlorine species such as hypochlorite. Additionally, this enzyme has a role in modulating the host immune response to infection. Here, we have analysed the enzymatic properties of MsrAB, which revealed that both domains of the protein are catalytically active, with the turnover number of the MsrA domain being 50% greater than that for the MsrB domain. MsrAB was active with small molecular sulfoxides as well as oxidised calmodulin, and maximal activity was observed at 30°C, a temperature close to that found in the natural niche of H. influenzae, the nasopharynx. Analyses of differential methionine oxidation identified 29 outer membrane and periplasmic proteins that are likely substrates for MsrAB. These included the LldD lactate dehydrogenase and the lipoprotein eP4 that is involved in NAD and hemin metabolism in H. influenzae. Subsequent experiments showed that H. influenzae MsrAB can repair oxidative damage to methionines in purified eP4 with up to 100% efficiency. Our work links MsrAB to the maintenance of different adhesins and essential metabolic processes in the H. influenzae, such as NAD metabolism and access to L-lactate, which is a key growth substrate for H. influenzae during infection.

The DmsABC S-oxide reductase is an essential component of a novel, hypochlorite-inducible system of extracellular stress defense in Haemophilus influenzae

“…In addition to DmsABC, H. influenzae strains contain two other periplasmic sulfoxide reductases, the MtsZ methionine sulfoxide reductase and the MsrAB peptide methionine sulfoxide reductase ( Dhouib et al, 2016 ; Nasreen et al, 2020 , 2022 ). The three enzymes reduce either protein-bound methionine sulfoxide (MsrAB) or free S-/N-oxides (MtsZ, DmsABC), and their expression is upregulated when the bacteria are exposed to hypochlorite ( Dhouib et al, 2016 ; Nasreen et al, 2020 ).…”

TheHaemophilus influenzaein vivo gene expression reveals major clues about bacterial central metabolism, acquisition of trace elements, and other essential pathways during infection of the human lung

“…Lack of the gene also caused diminished survival in biofilm as well as lower invasive potential in vitro and in a mouse model (75). Surprisingly, MsrAB activity has been shown to be highest in temperatures of 30 degrees and lower (76). Our results indicate that transcription of msrAB is of importance for persistence in the human respiratory system, and that is not overtly affected by temperatures of 37 degrees and higher, as would be commonly encountered in the febrile human body.…”

Emergentemm4group AStreptococcusevidences a survival strategy during interaction with immune effector cells

“…In Streptococcus pneumoniae, the msrAB operon encodes proteins that are surface localized and shown to be specifically involved in response to extracellular but not intracellular oxidative stress [59][60][61]. Therefore, to determine whether the emergent strains were specifically resistant to extracellular oxidative stress, the strains were exposed to paraquat which induces the formation of reactive oxygen species (ROS), such as superoxide, in the cytoplasm in the presence of oxygen [60].…”