Cr. Rhodes et al., Structural consequences of divalent metal binding by the adenylyl cyclase toxin of Bordetella pertussis, ARCH BIOCH, 395(2), 2001, pp. 169-176
Adenylyl cyclase toxin of Bordetella pertussis has been shown by several in
vestigators to require Ca2+ for its actions on target cells, but little is
known about the nature and specificity of divalent metal binding to this no
vel toxin. Calcium is the preferred divalent metal since toxic actions are
markedly reduced in the presence of divalent species other than calcium. Mn
2+ EPR was used to quantitate and characterize divalent metal binding and r
evealed that the toxin contains approximately 40 divalent metal sites, cons
isting of at least one class of high-affinity sites that bind Mn2+ with a K
-D of 0.05 to 0.35 muM and one or more classes of lower affinity sites. Wat
er proton relaxation data indicate that approximately 30 of these sites are
completely inaccessible to bulk solvent. Our observations, together with t
he sequence homology between adenylyl cyclase toxin and the alkaline protea
se of Pseudomonas aeruginosa, indicate that the formation of five beta -she
et helices within the repeat domain of the toxin upon binding C2+ is requir
ed for cell intoxication. (C) 2001 Academic Press.