TABLE 1

Strains and plasmids used in this study

Strain or plasmidRelevant characteristics or useReference or source
C. diphtheriae strains
    1737Wild type, Gravis biotype, tox+24
    1737htaAΔhtaA deletion mutant of 17375
    1737hmuTUVΔhmuTUV deletion mutant of 17375
    1737hmuΔhmu operon deletion mutant of 17375
    1737chtAΔchtA deletion mutant of 173720
    1737chtCΔchtC deletion mutant of 173720
    1737chtAΔ/chtCΔ/htaAΔDeletion of chtA, chtC, and htaA in 173720
    1737chtAΔ/chtCΔDeletion of chtA and chtC in 173720
    C7 (−)Wild type, tox negative36
    1716Wild type, Gravis biotype, tox+24
    1718Wild type, Gravis biotype, tox+24
    G4193Wild type, tox negative24
    PW8Wild type, tox+ U.S. vaccine strain37
E. coli strains
    BL21(DE3)Protein expressionNovagen
    DH5αCloning strainInvitrogen
    XL1-GoldMutagenesis strainStratagene
Plasmids
    pGEX-6P-1Expression vector (GST fusion); AmprGE Healthcare
    pET24(a)+Expression vector; KnrMillipore
    pKN2.6ZC. diphtheriae shuttle vector; Knr23
    pKN-htaApKN2.6Z carrying the htaA gene5
    pKNQ-cyspKN-htaA, Cys to AlaaThis study
    pKN-htaA361pKN-htaA with Y361A mutation19
  • a The four cysteine residues in HtaA were changed to alanine.