Identification of the cDNA for Human Red Blood Cell – Specific

A unique cDNA for hexokinase (HK) was identified from the observation that HKR activity is predominant in reticulopoly(A) RNA of human reticulocytes by anchored polymercytes. Northern blot analysis showed that it was expressed ase chain reaction. This appeared to represent the cDNA for in the reticulocytes and in the K562 erythroleukemic cell line, the red blood cell (RBC)–specific HK isozyme (HKR) described but not in a lymphocytic cell line. In the extract of K562 cells, in our previous study (Murakami et al: Blood 75:770, 1990). HKR activity co-eluted with the HKR of human RBCs on a Its nucleotide sequence was identical to HKI cDNA except MonoQ column (Pharmacia, Piscataway, NJ) chromatografor the 5* extreme end. It lacked the first 62 nucleotides of the phy, using a salt gradient elution. The separate genetic conHKI coding region: instead, it contained a unique sequence of trol of the RBC-specific HK isozyme explains the clinical re60 nucleotides at the beginning of the coding sequence as ports of two types of HK deficiency, one in which the HK well as another unique sequence upstream of the putative activity was reduced exclusively in the RBC (HKR defect) and translation initiation site. It lacked the porin-binding domain another with general decrease of HK activity in several tiswhich facilitates binding to the mitochondria, thus exsues (HKI defect). plaining the exclusive cytoplasmic localization of HKR. It was q 1997 by The American Society of Hematology. the major cDNA derived from reticulocytes, consistent with