FIGURE 3.

MALDI MS of chymotryptic digests identified NEM- and NFMhyd-labeled fragments of ND3. A, MS of protein spot 2 (Fig. 2) from NEM-labeled complex I. [a.u.], counts in absolute units. B, MS of fluorescent-labeled protein from spot 1 (Fig. 2). Signals that could be assigned to labeled fragments ECGFDPMGSARLPF and SEKTSPYECGFDPMGSARLPF of the ND3 subunit of complex I are boxed. Signals that could be assigned to chymotryptic ND3 fragments in general are marked with a strong dot on the tip. Non-assignable signals are marked with a smaller dot (see also supplemental Tables S3 and S4). Signals corresponding to background are not marked (see also “Experimental Procedures” and supplemental Table S5).