title: Tyrosine phosphorylation enhances activity of pneumococcal autolysin LytA.
abstract: Tyrosine phosphorylation has long been recognized as a crucial post-translational regulatory mechanism in eukaryotes. However, only in the past decade has recognition been given to the crucial importance of bacterial tyrosine phosphorylation as an important regulatory feature of pathogenesis. This study describes the effect of tyrosine phosphorylation on the activity of a major virulence factor of the pneumococcus, the autolysin LytA, and a possible connection to the Streptococcus pneumoniae capsule synthesis regulatory proteins (CpsB, CpsC and CpsD). We show that in vitro pneumococcal tyrosine kinase, CpsD, and the protein tyrosine phosphatase, CpsB, act to phosphorylate and dephosphorylate LytA. Furthermore, this modulates LytA function in vitro with phosphorylated LytA binding more strongly to the choline analogue DEAE. A phospho-mimetic (Y264E) mutation of the LytA phosphorylation site displayed similar phenotypes as well as an enhanced dimerization capacity. Similarly, tyrosine phosphorylation increased LytA amidase activity, as evidenced by a turbidometric amidase activity assay. Similarly, when the phospho-mimetic mutation was introduced in the chromosomal lytA of S. pneumoniae, autolysis occurred earlier and at an enhanced rate. This study thus describes, to our knowledge, the first functional regulatory effect of tyrosine phosphorylation on a non-capsule-related protein in the pneumococcus, and suggests a link between the regulation of LytA-dependent autolysis of the cell and the biosynthesis of capsular polysaccharide.
authors.affiliation: School of Molecular and Biomedical Sciences, University of Adelaide, SA 5005, Australia.
authors.forename: Alistair J
authors.initials: AJ
authors.lastname: Standish
authors.affiliation: School of Molecular and Biomedical Sciences, University of Adelaide, SA 5005, Australia.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Whittall
authors.affiliation: School of Molecular and Biomedical Sciences, University of Adelaide, SA 5005, Australia.
authors.forename: Renato
authors.initials: R
authors.lastname: Morona
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001433:Bacteriolysis; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D013296:Streptococcus pneumoniae / Q000201:enzymology* / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism*; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors; D014443:Tyrosine; D009238:N-Acetylmuramoyl-L-alanine Amidase