title: Identification of a crucial residue required for Staphylococcus aureus LukAB cytotoxicity and receptor recognition.
abstract: The bicomponent leukotoxins produced by Staphylococcus aureus kill host immune cells through osmotic lysis by forming β-barrel pores in the host plasma membrane. The current model for bicomponent pore formation proposes that octameric pores, comprised of two separate secreted polypeptides (S and F subunits), are assembled from water-soluble monomers in the extracellular milieu and multimerize on target cell membranes. However, it has yet to be determined if all staphylococcal bicomponent leukotoxin family members exhibit these properties. In this study, we report that leukocidin A/B (LukAB), the most divergent member of the leukotoxin family, exists as a heterodimer in solution rather than two separate monomeric subunits. Notably, this property was found to be associated with enhanced toxin activity. LukAB also differs from the other bicomponent leukotoxins in that the S subunit (LukA) contains 33- and 10-amino-acid extensions at the N and C termini, respectively. Truncation mutagenesis revealed that deletion of the N terminus resulted in a modest increase in LukAB cytotoxicity, whereas the deletion of the C terminus rendered the toxin inactive. Within the C terminus of LukA, we identified a glutamic acid at position 323 that is critical for LukAB cytotoxicity. Furthermore, we discovered that this residue is conserved and required for the interaction between LukAB and its cellular target CD11b. Altogether, these findings provide an in-depth analysis of how LukAB targets neutrophils and identify novel targets suitable for the rational design of anti-LukAB inhibitors.
authors.affiliation: Department of Microbiology, New York University School of Medicine, New York, New York, USA.
authors.forename: Ashley L
authors.initials: AL
authors.lastname: DuMont
authors.forename: Pauline
authors.initials: P
authors.lastname: Yoong
authors.forename: Xiang
authors.initials: X
authors.lastname: Liu
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Day
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Chumbler
authors.forename: David B A
authors.initials: DB
authors.lastname: James
authors.forename: Francis
authors.initials: F
authors.lastname: Alonzo
authors.forename: Nadine J
authors.initials: NJ
authors.lastname: Bode
authors.forename: D Borden
authors.initials: DB
authors.lastname: Lacy
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jennings
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Torres
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D039481:CD11b Antigen / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D005098:Exotoxins / Q000378:metabolism; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D007956:Leukocidins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D013203:Staphylococcal Infections / Q000235:genetics / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D039481:CD11b Antigen; D005098:Exotoxins; C509295:ITGAM protein, human; D007956:Leukocidins; C586430:leukocidin AB, Staphylococcus aureus; C018579:leukotoxin; D018698:Glutamic Acid