Functional importance of the Gly cluster in transmembrane helix 2 of the Bordetella pertussis CyaA-hemolysin: implications for toxin oligomerization and pore formation.

Functional importance of the Gly cluster in transmembrane helix 2 of the Bordetella pertussis CyaA-hemolysin: implications for toxin oligomerization and pore formation. Toxicon. 2015 Sep 9; Authors: Juntapremjit S, Thamwiriyasati N, Kurehong C, Prangkio P, Shank L, Powthongchin B, Angsuthanasombat C Abstract Adenylate cyclase-hemolysin (CyaA) is a major virulence factor of Bordetella pertussis causing whooping cough in humans. We previously showed that two transmembrane helices (α2 and α3) in the hemolysin domain (CyaA-Hly) are crucially involved in hemolytic activity. Here, PCR-based substitutions were employed to investigate a potential involvement in hemolysis of a series of four Gly residues (Gly(530), Gly(533), Gly(537) and Gly(544)) which map onto one face of a helical wheel plot of pore-lining helix 2. All CyaA-Hly mutant toxins were over-expressed in Escherichia coli as 126-kDa soluble proteins at levels comparable to the wild-type toxin. A drastic reduction in hemolytic activity against sheep erythrocytes was observed for three CyaA-Hly mutants, i.e. G530A, G533A and G537A, but not G544A, suggesting a functional importance of the Gly(530)_Gly(533)_Gly(537) cluster. A homology-based structure of the α2-loop-α3 hairpin revealed that this crucial Gly cluster arranged as a GXXGXXXG motif is conceivably involved in helix-helix association. Furthermore, a plausible pore model comprising three α2-loop-α3 hairpins implicated t...
Source: Toxicon - Category: Toxicology Authors: Tags: Toxicon Source Type: research