title: Metal-mediated modulation of streptococcal cysteine protease activity and its biological implications.
abstract: Streptococcal cysteine protease (SpeB), the major secreted protease produced by group A streptococcus (GAS), cleaves both host and bacterial proteins and contributes importantly to the pathogenesis of invasive GAS infections. Modulation of SpeB expression and/or its activity during invasive GAS infections has been shown to affect bacterial virulence and infection severity. Expression of SpeB is regulated by the GAS CovR-CovS two-component regulatory system, and we demonstrated that bacteria with mutations in the CovR-CovS two-component regulatory system are selected for during localized GAS infections and that these bacteria lack SpeB expression and exhibit a hypervirulent phenotype. Additionally, in a separate study, we showed that expression of SpeB can also be modulated by human transferrin- and/or lactoferrin-mediated iron chelation. Accordingly, the goal of this study was to investigate the possible roles of iron and other metals in modulating SpeB expression and/or activity in a manner that would potentiate bacterial virulence. Here, we report that the divalent metals zinc and copper inhibit SpeB activity at the posttranslational level. Utilizing online metal-binding site prediction servers, we identified two putative metal-binding sites in SpeB, one of which involves the catalytic-dyad residues (47)Cys and (195)His. Based on our findings, we propose that zinc and/or copper availability in the bacterial microenvironment can modulate the proteolytic activity of SpeB in a manner that preserves the integrity of several other virulence factors essential for bacterial survival and dissemination within the host and thereby may exacerbate the severity of invasive GAS infections.
authors.affiliation: Department of Molecular Genetics, Biochemistry and Microbiology, College of Medicine, University of Cincinnati, Cincinnati, Ohio, USA Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota, USA.
authors.forename: Karthickeyan
authors.initials: K
authors.lastname: Chella Krishnan
authors.affiliation: Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota, USA.
authors.forename: Santhosh
authors.initials: S
authors.lastname: Mukundan
authors.affiliation: University of Cincinnati/Agilent Technologies Metallomics Center of the Americas, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio, USA.
authors.forename: Julio A
authors.initials: JA
authors.lastname: Landero Figueroa
authors.affiliation: University of Cincinnati/Agilent Technologies Metallomics Center of the Americas, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Caruso
authors.affiliation: Department of Molecular Genetics, Biochemistry and Microbiology, College of Medicine, University of Cincinnati, Cincinnati, Ohio, USA Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota, USA Veterans Affairs Hospital, Cincinnati, Ohio, USA malak.kotb@med.und.edu.
authors.forename: Malak
authors.initials: M
authors.lastname: Kotb
mesh_terms: D003300:Copper / Q000494:pharmacology*; D057056:Cysteine Proteases / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects* / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects* / Q000502:physiology; D008670:Metals / Q000494:pharmacology; D004369:Pentetic Acid / Q000008:administration & dosage / Q000494:pharmacology; D040901:Proteomics; D013297:Streptococcus pyogenes / Q000201:enzymology* / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology*
chemical_list: D008670:Metals; D037521:Virulence Factors; D003300:Copper; D004369:Pentetic Acid; D057056:Cysteine Proteases; D015032:Zinc