Metal substitution of tetanus neurotoxin.
Tetanus neurotoxin was depleted of its catalytic Zn2+ ion, and the apotoxin was reconstituted with different transition metal ions. The Mn2+- and Co2+-tetanus neurotoxins are highly active in the proteolysis of vesicle-associated membrane protein/synaptobrevin, the natural substrate of this toxin, whereas Cu2+ and Fe2+ minimally supported proteolytic activity. The visible absorbance spectrum of Co2+-tetanus neurotoxin shows a maximum at 538 nm with a molar absorption coefficient of 82 M(-1) x cm(-1). These results indicate that the Zn2+ environment at the active site of tetanus neurotoxin is different from those of known Zn2+-endopeptidases and provide a structural basis for the definition of tetanus neurotoxin, and the related clostridial neurotoxins, as an independent family of metalloproteases.
Tonello
F
F
Centro C.N.R. Biomembrane and Dipartimento di Scienze Biomediche, Universita di Padova, Italy.
Schiavo
G
G
Montecucco
C
C
D001665:Binding Sites; D008565:Membrane Proteins / Q000378:metabolism; D008666:Metalloendopeptidases / Q000737:chemistry* / Q000378:metabolism; D019216:Metals, Heavy; D050683:R-SNARE Proteins; D013053:Spectrophotometry; D013744:Tetanus Toxin / Q000737:chemistry* / Q000378:metabolism
D008565:Membrane Proteins; D019216:Metals, Heavy; D050683:R-SNARE Proteins; D013744:Tetanus Toxin; C035979:tetanospasmin; D008666:Metalloendopeptidases