Inhibition of catalytic activities of botulinum neurotoxin light chains of serotypes A, B and E by acetate, sulfate and calcium

International Journal of Biochemistry and Molecular Biology

S Swaminathan¹  Rahman M Mizanur¹  S Ashraf Ahmed¹  John Gorbet¹ 

关键词: Botulinum neurotoxin;    endopeptidase;    protease;    active site;    inhibitor;    small molecule;   

DOI  :  

学科分类：生物化学/生物物理

来源: e-Century Publishing Corporation

【 摘 要 】

The catalytic domain, known as light chain (Lc), of the most poisonous botulinum neurotoxins (BoNTs), possesses endoprotease activity that triggers the ultimate poisonous effect to animals and humans. X-ray crystallographic structure of Lc of several BoNT serotypes has identified at least four small ligands at or near the respective active sites. They are sulfate ions in LcA, LcB, and LcE; an acetate ion in LcA; a calcium ion in LcB; and a potassium ion in LcD. Roles of these ligands on the structure and function of the proteins are not known. We have investigated the roles of sulfate, acetate, and calcium on the catalytic activities of LcA, LcB, and LcE using 17-35-residue synthetic peptide substrates. All three ligands inhibited all Lc activities. For LcA and LcB, the order of inhibition effectiveness was calcium>sulfate>acetate. The inhibition effectiveness expressed as IC₅₀, did not correlate with the occurrence or proximity of the ions to the active site. Moreover, addition of acetate or sulfate to LcA did not affect the near-UV circular dichroism spectra, tryptophan, and tyrosine fluorescence spectra, and mid points of thermal denaturation of LcA. Our results suggest that acetate, sulfate, and calcium nonspecifically interact with BoNT Lc, and their occurrence in the crystal structures could have been due to opportunistic binding to complementary pockets.

【 授权许可】

Unknown