The Exoproteome\nand Surfaceome of Toxigenic Corynebacterium diphtheriae 1737 and Its Response\nto Iron Restriction and Growth on Human Hemoglobin

Toxin-producing Corynebacterium\ndiphtheriae strains are the etiological agents of\nthe severe upper respiratory\ndisease, diphtheria. A global phylogenetic analysis revealed that\nbiotype gravis is particularly lethal as it produces diphtheria toxin\nand a range of other virulence factors, particularly when it encounters\nlow levels of iron at sites of infection. To gain insight into how\nit colonizes its host, we have identified iron-dependent changes in\nthe exoproteome and surfaceome of C. diphtheriae strain 1737 using a combination of whole-cell fractionation, intact\ncell surface proteolysis, and quantitative proteomics. In total, we\nidentified 1414 of the predicted 2265 proteins (62%) encoded by its\nreference genome. For each protein, we quantified its degree of secretion\nand surface exposure, revealing that exoproteases and hydrolases predominate\nin the exoproteome, while the surfaceome is enriched with adhesins,\nparticularly DIP2093. Our analysis provides insight into how components\nin the heme-acquisition system are positioned, showing pronounced\nsurface exposure of the strain-specific ChtA/ChtC paralogues and high\nsecretion of the species-conserved heme-binding HtaA protein, suggesting\nit functions as a hemophore. Profiling the response of the exoproteome\nand surfaceome after microbial exposure to human hemoglobin and iron\nlimitation reveals potential virulence factors that may be expressed\nat sites of infection. Data are available via ProteomeXchange with\nidentifier PXD051674.