Dioxin binding activities of polymorphic forms of mouse and human arylhydrocarbon receptors.

摘要: The genetic difference in the susceptibility of mice to environmental toxicities induced by dioxin and related chemicals is governed polymorphism arylhydrocarbon receptor (AhR) (Poland, A., Knutson, C. (1982) Annu. Rev. Pharmacol. Toxicol. 22, 517-554). cDNA cloning AhR from responder (C57BL/6) non-responder (DBA/2J) allowed us analyze structure function these AhRs. Both AhRs, which were expressed COS-7 cells transfected with their expression plasmids, showed a clear 9 S complex 2,3,7,8-[3H]tetrachlorodibenzo-p-dioxin (TCDD) linear glycerol gradient centrifugation, consistent result endogenously Hepa-1 cells. This provides first direct evidence that cDNA-encoded protein binds ligand specifically. Scatchard plot analysis revealed dissociation constant (Kd) C57BL for TCDD 0.27 nM, while DBA elevated up six times high. Chimeric plasmids between two cDNAs site-directed mutagenesis critical alterations responsible reduced binding activity: an Ala375 Val alteration elongated carboxyl-terminal sequence due T C mutation at letter termination codon AhR. Two variants intermediate activity also found human AhRs amino acid equivalent those Importance position 381 (equivalent 375 mouse AhR) was confirmed fact Val381 Asp completely abolished