CorA purification. (a) Coomassie-stained SDS–PAGE of purified M. mazei CorA. Lane MW, molecular-weight markers (170, 130, 100, 70, 55, 40, 35, 25, 15 and 10 kDa); lane CorA, two-step purified M. mazei CorA. (b) Peptide mass-fingerprint MALDI–TOF identification using the sequence of M. mazei CorA and the band shown in Fig. 2 ▶(a). The sequence coverage was 35.5%. Grey bars indicate matching peptides.