title: Genetic characterization and virulence role of the RALP3/LSA locus upstream of the streptolysin s operon in invasive M1T1 Group A Streptococcus.
abstract: Group A Streptococcus (GAS) is a leading human pathogen associated with a wide spectrum of mucosal and invasive infections. GAS expresses a large number of virulence determinants whose expression is under the control of several transcriptional regulatory networks. Here we performed the first mutational analysis of a genetic locus immediately upstream of the streptolysin S biosynthetic operon in several GAS genome sequences, including that of the M1T1 serotype, the leading isolates associated with serious invasive disease. The locus consists of a predicted RofA-like stand-alone transcriptional regulator (RALP3) and the largest open reading frame in the GAS genome, encoding a predicted LPXSG motif cell wall-anchored protein we have named LSA (for "large surface-anchored" protein). Comparative reverse transcription-PCR analysis of wild-type M1T1 GAS and an isogenic RALP3-deficient mutant identifies RALP3 as a global transcriptional regulator affecting expression of numerous virulence factor genes, including those for strong repression of the hyaluronic acid capsule and cysteine protease production. RALP3 contributed to GAS epithelial cell invasion and bloodstream survival. LSA was found to be under negative regulation by RALP3 and to influence GAS-epithelial cell interactions and GAS antimicrobial peptide sensitivity. Isogenic M1T1 GAS mutants lacking either RALP3 or LSA were attenuated in a murine model of systemic infection, indicating that this locus plays a role in the virulence potential of the organism.
authors.affiliation: Department of Pediatrics, Division of Pharmacology & Drug Discovery, University of California, San Diego School of Medicine, Cellular & Molecular Medicine East, La Jolla, CA 92093-0687, USA.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Kwinn
authors.forename: Arya
authors.initials: A
authors.lastname: Khosravi
authors.forename: Ramy K
authors.initials: RK
authors.lastname: Aziz
authors.forename: Anjuli M
authors.initials: AM
authors.lastname: Timmer
authors.forename: Kelly S
authors.initials: KS
authors.lastname: Doran
authors.forename: Malak
authors.initials: M
authors.lastname: Kotb
authors.forename: Victor
authors.initials: V
authors.lastname: Nizet
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D003470:Culture Media; D003546:Cysteine Endopeptidases / Q000378:metabolism; D005260:Female; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism; D051379:Mice; D009876:Operon / Q000235:genetics*; D013297:Streptococcus pyogenes / Q000235:genetics* / Q000472:pathogenicity*; D013301:Streptolysins / Q000235:genetics / Q000378:metabolism*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D013301:Streptolysins; C026050:streptolysin S; D006820:Hyaluronic Acid; D003546:Cysteine Endopeptidases