Figure 2. The soluble and insoluble fractions of recombinant BCL-XL produced in E. coli have different molecular masses.
(A) SDS-PAGE showing expression of wild-type (wt) or Met218 mutant (M218L) BCL-XL (arrow) in the soluble (s) and insoluble (i) E. coli cell fractions. Gels were stained with Coomassie blue. Molecular weight markers are shown in left lane (m). (B) MALDI mass spectra of 15N-labeled proteins purified from soluble (s) or insoluble (i) cell fractions. Molecular mass is given in atomic mass units (amu) derived from mass to charge (m/z) ratio.