Figure 5.

Substrate loading analysis using MALDI-TOF MS. MALDI mass spectrum of KS and mutant proteins with or without N-2,2-dimethylacetoacetyl-l-Ile-SNAC reacted for 12 h in 2 mm Tris-HCl, pH 7.5. The m/z of the detected protein–substrate complex is shown in red characters. Spectrum peaks with and without substrate are shown in green and yellow, respectively. Theoretical molecular weight (Da): KS WT, 47,959; C179A, 47,927; and H322F, 47969. The molecular weight of N-2,2-dimethylacetoacetyl-l-Ile, 227.