Western blot analysis of exon deletion ferrochelatase mutants. Cell extracts of the exon deletion and wild-type human ferrochelatases containing about 5 μg were separated by SDS-polyacrylamide gel electrophoresis, transferred to a nitrocellulose membrane, and treated with human ferrochelatase antiserum. Procedures are as stated in Materials and Methods. From right to left, lanes 1 and 2, wild-type human ferrochelatase used as control; lanes 3 through 11, ▵exon 3 through ▵exon 11 in sequential order. Exons 3 and 4 are believed to contain the epitope for antibody recognition. The size differences of these proteins are evident as the mature-length wild-type human ferrochelatase (from pHDTF20) has a molecular weight of 42 kD and contains 363 amino acid residues, ▵exon 5 contains 320 residues, ▵exon 6 contains 331 residues, ▵exon 7 contains 333 residues, ▵exon 8 contains 330, ▵exon 9 contains 310, ▵exon 10 contains 347, and ▵exon 11 contains 318 residues.