M. A. Meehl, J. S. Pinkner, P. J. Anderson, S. J. Hultgren and M. G. Caparon, “A Novel Endogenous Inhibitor of the Secreted Streptococcal NAD-Glycohydrolase,” PLoS Pathogens, Vol. 1, No. 4, 2005, p. e35. doi:10.1371/journal.ppat.0010035

has been cited by the following article:

• TITLE: Characterization of NADase-Inactive NAD+ Glycohydrolase in Streptococcus pyogenes

  AUTHORS: Ichiro Tatsuno, Masanori Isaka, Tadao Hasegawa

  KEYWORDS: Streptococcus pyogenes ; NAD+ Glycohydrolase; NADase; SPN; Streptococcal; SF370

  JOURNAL NAME: Advances in Microbiology, Vol.3 No.1, March 28, 2013

  ABSTRACT: Background: Streptococcus pyogenes secretes NAD+ glycohydrolase (NADase, also known as SPN or Nga). All S. pyogenes strains examined to date possess the gene that encodes SPN (spn), but some strains produce SPN that lacks detectable NADase activity. Although there is much evidence to support that SPN’s NADase activity contributes to virulence, there is very little evidence that NADase-inactive SPN has detectable functions. Results: In order to characterize the NADase-inactive SPN, we firstly attempted to clone the NADase-inactive spn allele in Escherichia coli. Although we obtained recombinants which were shown to have the correct size insert, all had some mutations in the spn allele. Therefore, we attempted to change the mutated nucleotides back to the original nucleotides. While a nucleotide mutagenesis (inverse PCR method) easily changed a target nucleotide of control genes back to the original nucleotides, the mutations of NADase-inactive spn allele were never successfully converted back to the original nucleotides. Finally the mutant spn alleles were sub-cloned into another vector (pLZ12-Km2), which is maintained in both E. coli and S. pyogenes. The resultant plasmids were subjected to nucleotide mutagenesis using inverse PCR; the resultant mutagenized plasmid DNAs were used to transform both E. coli and S. pyogenes strains. We observed successful nucleotide substitutions back to the original spn nucleotide sequence in S. pyogenes transformants, but not in E. coli transformants. Thus, the NADase-inactive spn allele was successfully cloned in S. pyogenes, but not in E. coli. However, we could not find an association with NADase-inactive spn allele and virulence in a mouse infection model. Conclusions: These results suggest that NADase-inactive spn allele has some toxic effect to E. coli, but not S. pyogenes. This effect may due to an as of yet unknown function attributable to NADase-inactive SPN.