Immunoblot analysis of ALAS-E protein in bone marrow cells of a pyridoxine-refractory XLSA patient. Expression of ALAS-E in rat reticulocytes and human bone marrow erythroid cells was analyzed with a rabbit antirat ALAS-N polyclonal antibody. Lanes 1 and 2 are loaded with a cytosolic fraction of rat liver and a whole homogenate of rat reticulocytes, respectively. A 77-kD precursor form of ALAS-N is detected in rat liver (lane 1, upper band), and the mature form of ALAS-E in rat reticulocytes (lane 2). Lane 3 contains a mitochondrial fraction of K562H cells and human ALAS-E can be detected (lane 3). Lanes 4 and 5 are loaded with a whole homogenate of bone marrow cells. Normal levels of ALAS-E are present in the bone marrow cells of an iron deficiency anemia patient (lane 4), but only about 5% of the level of normal controls are detectable in those of a pyridoxine-refractory XLSA patient (lane 5).