Molecular cloning and sequencing of myosin light chains in human megakaryoblastic leukemia cells

Myosin light chain genes of hematopoietic cells have yet to be characterized. We cloned the full-length cDNAs of 20 kDa regulatory myosin light chain (MLC-2) and 17 kDa essential myosin light chain (MLC-3) from Meg-01, a human megakaryoblastic leukemia cell line. Both MLC-2 and MLC-3 gene are transcribed ubiquitously in various hematopoietic cells. The MLC-2 open reading frame of 516 nucleotides encoding a protein of 172 residues was detected in cloned cDNA of 967 nucleotides. The Ca2+-binding domain and five phosphorylation sites were highly conserved. The deduced amino acid sequence has a 99.4% and 100% homology with that of human fetus brain and human lymphocyte, respectively. The MLC-3 open reading frame of 453 nucleotides encoding a protein of 151 residues was detected in cloned cDNA of 742 nucleotide. The MLC-3 protein is 99.3% identical to that of human fibroblasts. These results suggest that hematopoietic myosin light chain proteins are similar to those of other nonmuscle cells and smooth muscle, thus differing from skeletal and cardiac muscles.