Structural basis for the interaction of Bordetella pertussis adenylyl cyclase toxin with calmodulin.
CyaA is crucial for colonization by Bordetella pertussis, the etiologic agent of whooping cough. Here we report crystal structures of the adenylyl cyclase domain (ACD) of CyaA with the C-terminal domain of calmodulin. Four discrete regions of CyaA bind calcium-loaded calmodulin with a large buried contact surface. Of those, a tryptophan residue (W242) at an alpha-helix of CyaA makes extensive contacts with the calcium-induced, hydrophobic pocket of calmodulin. Mutagenic analyses show that all four regions of CyaA contribute to calmodulin binding and the calmodulin-induced conformational change of CyaA is crucial for catalytic activation. A crystal structure of CyaA-calmodulin with adefovir diphosphate, the metabolite of an approved antiviral drug, reveals the location of catalytic site of CyaA and how adefovir diphosphate tightly binds CyaA. The ACD of CyaA shares a similar structure and mechanism of activation with anthrax edema factor (EF). However, the interactions of CyaA with calmodulin completely diverge from those of EF. This provides molecular details of how two structurally homologous bacterial toxins evolved divergently to bind calmodulin, an evolutionarily conserved calcium sensor.
Guo
Qing
Q
Ben-May Institute for Cancer Research, The University of Chicago, Chicago, IL 60637, USA.
Shen
Yuequan
Y
Lee
Young-Sam
YS
Gibbs
Craig S
CS
Mrksich
Milan
M
Tang
Wei-Jen
WJ
D037361:Adenylate Cyclase Toxin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001886:Bordetella pertussis / Q000201:enzymology* / Q000235:genetics; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D014757:Viper Venoms / Q000737:chemistry / Q000378:metabolism
D037361:Adenylate Cyclase Toxin; D002147:Calmodulin; D009711:Nucleotides; D014757:Viper Venoms; C416405:edema factor