Table 3: Relative Abundances and Masses of PspE Species Found in Purified Fractions PspE1 and Ps

Enzyme form a
(theoretical mass)		 Enzyme Fraction
PspE1 PspE2 PspE2 b + SSO32-
Abundance c Mass Abundance Mass Abundance Mass
E-SH (9427.7) 0.23 9427.9 0.6 9427.8 0.25 9427.6
E-SSH (9459.76) 0.57 9459.9 1 9460.1 0.65 9460.3
E-SSSH (9491.83) 1 9492.2 0.32 9491.9 0.71 9492.4
E-SSO3H (9507.76) 0.67 9507.9 0.6 9507.8 1 9507.9
E-SSSO3H (9539.83) <0.1 -- <0.1 -- 0.38 9540.5

a The species of PspE observed in the mass spectral analysis are consistent with those indicated, with E-SH being the unmodified form of PspE. E-SSH is PspE containing the cys-teine persulfide, E-SSSH is the enzyme with two additional sulfur atoms, E-SSO3H is the form with a sulfonate modification and E-SSSO3H is the persulfide form with a sulfonate modification. The theoretical masses shown in parentheses are those calculated based on the amino acid sequence of processed (secreted) PspE as deduced from the DNA sequence.
b An aliquot of fraction PspE2 was treated with 1 mM ammonium thiosulfate as described in “Methods.”
c The average abundances of the major peaks observed in the mass spectra, relative to the most abundant peak observed (designated 1.00), are shown. The molecular masses for each peak were calculated by averaging the masses obtained by deconvolution of the spectra observed for the +10, +11, +12 and +13 molecular ions.