Anthrax toxin receptor 2 determinants that dictate the pH threshold of toxin pore formation.
The anthrax toxin receptors, ANTXR1 and ANTXR2, act as molecular clamps to prevent the protective antigen (PA) toxin subunit from forming pores until exposure to low pH. PA forms pores at pH approximately 6.0 or below when it is bound to ANTXR1, but only at pH approximately 5.0 or below when it is bound to ANTXR2. Here, structure-based mutagenesis was used to identify non-conserved ANTXR2 residues responsible for this striking 1.0 pH unit difference in pH threshold. Residues conserved between ANTXR2 and ANTXR1 that influence the ANTXR2-associated pH threshold of pore formation were also identified. All of these residues contact either PA domain 2 or the neighboring edge of PA domain 4. These results provide genetic evidence for receptor release of these regions of PA as being necessary for the protein rearrangements that accompany anthrax toxin pore formation.
Scobie
Heather M
HM
Infectious Disease Laboratory, The Salk Institute for Biological Studies, La Jolla, California, United States of America.
Marlett
John M
JM
Rainey
G Jonah A
GJ
Lacy
D Borden
DB
Collier
R John
RJ
Young
John A T
JA
D000595:Amino Acid Sequence; D000818:Animals; D000881:Anthrax / Q000235:genetics*; D000942:Antigens, Bacterial / Q000235:genetics; D001408:Bacillus anthracis / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D017124:Conserved Sequence; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D004705:Endocytosis / Q000235:genetics; D017930:Genes, Reporter; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000235:genetics; D016296:Mutagenesis; D010957:Plasmids / Q000235:genetics; D018000:Receptors, Peptide / Q000235:genetics*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D008565:Membrane Proteins; D018000:Receptors, Peptide; C070309:anthrax toxin receptors