title: LytA, major autolysin of Streptococcus pneumoniae, requires access to nascent peptidoglycan.
abstract: The pneumococcal autolysin LytA is a virulence factor involved in autolysis as well as in fratricidal- and penicillin-induced lysis. In this study, we used biochemical and molecular biological approaches to elucidate which factors control the cytoplasmic translocation and lytic activation of LytA. We show that LytA is mainly localized intracellularly, as only a small fraction was found attached to the extracellular cell wall. By manipulating the extracellular concentration of LytA, we found that the cells were protected from lysis during exponential growth, but not in the stationary phase, and that a defined threshold concentration of extracellular LytA dictates the onset of autolysis. Stalling growth through nutrient depletion, or the specific arrest of cell wall synthesis, sensitized cells for LytA-mediated lysis. Inhibition of cell wall association via the choline binding domain of an exogenously added enzymatically inactive form of LytA revealed a potential substrate for the amidase domain within the cell wall where the formation of nascent peptidoglycan occurs.
authors.affiliation: Department of Microbiology, Tumor, and Cell Biology, Karolinska Institutet, 17177 Stockholm, Sweden. peter.mellroth@ki.se
authors.forename: Peter
authors.initials: P
authors.lastname: Mellroth
authors.forename: Robert
authors.initials: R
authors.lastname: Daniels
authors.forename: Alice
authors.initials: A
authors.lastname: Eberhardt
authors.forename: Daniel
authors.initials: D
authors.lastname: Rönnlund
authors.forename: Hans
authors.initials: H
authors.lastname: Blom
authors.forename: Jerker
authors.initials: J
authors.lastname: Widengren
authors.forename: Staffan
authors.initials: S
authors.lastname: Normark
authors.forename: Birgitta
authors.initials: B
authors.lastname: Henriques-Normark
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001433:Bacteriolysis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D003840:Deoxycholic Acid / Q000494:pharmacology; D003902:Detergents / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010457:Peptidoglycan / Q000096:biosynthesis* / Q000378:metabolism*; D021382:Protein Sorting Signals; D021381:Protein Transport / Q000187:drug effects; D013296:Streptococcus pneumoniae / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D003902:Detergents; D010457:Peptidoglycan; D021382:Protein Sorting Signals; D003840:Deoxycholic Acid; D009238:N-Acetylmuramoyl-L-alanine Amidase