Assignment of NADH-cytochrome b5 reductase (DIA1 locus) to human chromosome 22

NADH-cytochrome b5 reductase (DIA1, EC. 1.6.2.2) from human fibroblasts and from Chinese hamster cells, both identified by immunologic studies, were clearly distinguished after polyacrylamide gel isoelectro-focusing followed by staining for NADH diaphorase activity. In thirteen independent man-hamster hybrids, the human enzyme DIA1 presented a positive correlation with the human chromosome G22. Eight hybrids were DIA1(+) G22(+) and five hybrids were DIA1(-) G22(-). These data agree with the recent assignment of DIA1 to chromosome G22 by Fisher et al. (1977a). We assume that this newly assigned locus codes for both soluble and microsomal forms of NADH-cytochrome b5 reductase.