FIG 3.
Zinc specifically binds to SpeB irrespective of the propeptide region. Shown are the results of SEC followed by ICP MS analyses of zinc (or copper)-bound proteins from bacterial (5448WT) supernatants mixed with 1 mM (final concentration) the metal cocktail CaCl2, MgCl2, MnCl2, CuSO4, and ZnSO4. Molecular mass markers are shown at the top, and the two regions (∼42 and 28 kDa) collected for identifications are boxed. The two regions were found to be the zymogen and the mature forms of SpeB through LC–MS-MS analysis, as shown in Fig. S1 and S2 in the supplemental material.