Identification and molecular characterization of acyl-CoA synthetase in human erythrocytes and erythroid precursors

Full-length cDNA species encoding two forms of acyl-CoA synthetase from a K -562 human erythroleukaemic cell line were cloned, sequenced and expressed. The first form, named long-chain acyl-CoA synthetase 5 (LACS5), was found to be a novel, unreported, human acyl-CoA synthetase with high similarity t o rat brain ACS2 (91% identical). The second form (66% identical with LACS5 ) was 97% identical with human liver LACS1. The LACS5 gene encodes a highly expressed 2.9 kb mRNA transcript in human haemopoietic stem cells from cor d blood, bone marrow, reticulocytes and fetal blood cells derived from feta l liver. An additional 6.3 kb transcript is also found in these erythrocyte precursors; 2.9 and 9.6 kb transcripts of LACS5 are found in human brain, but transcripts are virtually absent from human heart, kidney, liver, lung, pancreas, spleen and skeletal muscle. The 78 kDa expressed LACS5 protein u sed the long-chain fatty acids palmitic acid, oleic acid and arachidonic ac id as substrates. Antibodies directed against LACS5 cross-reacted with eryt hrocyte membranes. We conclude that early erythrocyte precursors express at least two different forms of acyl-CoA synthetase and that LACS5 is present in mature erythrocyte plasma membranes.