Ultracentrifugal Analysis of the Crystalline Toxin and Isolated Fractions of Clostridium botulinum Type A
Daniel A. Boroff 1, Robert Townend 1, Ursula Fleck 1, and Bibhuti R. DasGupta 1
From the
1 From the Albert Einstein Medical Center and the Eastern Regional Research Laboratory, Philadelphia, Pennsylvania
Following the chromatographic separation of the crystalline toxin of Clostridium botulinum type A into one fraction (
) containing 5 times the specific activity of the unfractionated preparation and a second fraction (ß), only feebly toxic, the native toxin and the two components were analyzed in the ultracentrifuge for homogeneity and Fraction
was analyzed for molecular weight. Under all experimental conditions, crystalline toxin resolved into two peaks with s20,w values of about 7 and 13, respectively. Fraction ß aggregated to a heavier component, with s20,w of 16 or 23 S, depending upon the pH and ionic strength of the solvent and the concentration of the protein. Fraction
, however, remained homogeneous. The molecular weight of Fraction
, as determined by Yphantis' method, was 128,000 ± 10%. This value is in reasonable agreement with the molecular weight of 150,000 established for this component on Sephadex G-200 columns by Andrews' method. The possibility that Fraction
is a polymer of lower molecular weight units cannot yet be ruled out, nor do we know whether ß is the inactive "subunit" proposed by Wagman, an inactive precursor as postulated by Bonventre and Kempe, or a nonspecific contaminant which crystallizes with the toxic
fraction.
Submitted on June 8, 1966