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A cryptic citrate transport gene (citA) from Salmonella typhimurium chromosome was cloned and its nucleotide sequence was determined. The cloned plasmid conferred citrate-utilizing ability on wild-type Escherichia coli, which cannot grow on citrate as the sole source of carbon. The resultant E. coli transformant was able to transport citrate. A 1,302-base-pair open reading frame with a preceding ribosomal binding site was found in the cloned DNA fragment. The 434-amino-acid protein that could be translated from this open reading frame is highly hydrophobic (69% nonpolar amino acid residues), consistent with the fact that the transport protein is an intrinsic membrane protein. The molecular weight of this protein was calculated to be 47,188. The gene sequence determined is highly homologous to those of Cit+ plasmid-mediated citrate transport gene, citA, from E. coli, the chromosomal citA gene from Citrobacter amalonaticus and the chromosomal cit+ gene from Klebsiella pneumoniae. The hydropathy profile of the deduced amino acid sequence suggests that this carrier has 12 hydrophobic segments, which may span the membrane lipid bilayer.

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Summary Copper deficiency in human is uncommon. We described a 7‐month‐old Japanese infant who developed copper deficiency while being fed milk formula alone, and exhibited neutropenia, sideroblastic anemia and bone changes resembling scurvy and osteoporosis. We treated her with oral copper solution. Within 7 days of treatment, neutrophils and reticulocyte counts remarkably increased. Anemia was corrected by 2 weeks after initiation of copper therapy. Bone radiography showed remarkable improvement, and the maturation arrest and cytoplasmic vacuoles in the early myeloid and erythroid series on the bone marrow examination had disappeared after copper therapy. The plasma and erythrocyte copper concentrations, and serum ceruloplasmin levels returned rapidly to normal range. The patient has been doing well after discontinuing copper supplements. Although there has been no report of copper deficiency in Japanese infants nourished with milk formula alone, marginal copper deficiency, which escapes clinical recognition and is spontaneously cured when solid foods are added, may not be so uncommon in Japan. The recommended daily intake of copper cannot be achieved, if a Japanese infant, especially a premature baby, is nourished with milk formula alone. Therefore, Japanese milk formula must be !supplemented with copper.