The Journal of biological chemistry
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Comparative Study
Sequence homology between the tyrosine-sensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase from Escherichia coli and hemerythrin from Sipunculida.
The first enzyme of the common aromatic biosynthetic pathway in Escherichia coli, the 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase, contains iron as an integral part of the polypeptide chain, and the enzyme shows an absorption maximum around 350 nm (McCandliss, R. J., and Herrmann, K. M. (1978) Proc. ⋯ The amino acid sequence of residues 10 to 18 of the enzyme from E. coli, His-Ile-Thr-Asp-Glu-Gln-Val-Leu-Met, is highly homologous to the sequence of residues 54 to 62 of hemerythrin from Phascolopsis gouldii, His-Phe-Leu-Asn-Glu-Gln-Val-Leu-Met. His54 and Glu58 of hemerythrin have previously been identified through x-ray and protein sequence analysis as iron ligands. We suggest that residues 10 to 18 of the E. coli enzyme represent part of the iron binding fold in this protein, and that His10 and Glu14 are iron ligands.
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The amino acid sequence of the sulfate-binding protein from Salmonella typhimurium LT2 was determined by automated sequenator analysis of whole protein and fragments derived by chemical and enzymatic cleavage of whole protein. The fragments were products of limited trypsin digestion at arginine, cleavage at tryptophan by BrNps-skatole and o-iodosobenzoic acid, digestion with the protease from Staphylococcus aureus V8 at Glu-X bonds, cleavage by hydroxylamine at Asn-Gly bonds, and subdigestion with trypsin, chymotrypsin, and the Staphylococcus protease. The COOH-terminal sequence was confirmed using carboxypeptidase B and amino acid analysis. The sulfate-binding protein was determined to contain a single polypeptide of 310 residues with a molecular weight of 34,667 calculated from the sequence.
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Comparative Study
Enzymatic reduction of hemoglobins M Milwaukee-1 and M Saskatoon by NADH-cytochrome b5 reductase and NADPH-flavin reductase purified from human erythrocytes.
Enzymatic reduction of the hemoglobin (Hb) M group was studied. Hb M Milwaukee-1 and Hb M Saskatoon were reduced by NADH-cytochrome b5 reductase highly purified from human erythrocytes. Hb M Saskatoon was also reduced by another enzyme in red cells, NADPH-flavin reductase. ⋯ It took 1/2 h and 10 h for the 50% reduction of Hb M Saskatoon and Hb M Milwaukee-1, respectively. These two methemoglobin reductases from erythrocytes did not reduce other hemoglobins M such as Hb M Iwate, Hb M Boston, or Hb M Hyde Park. A possible role of these abnormal hemoglobins as oxygen carriers and the reason for cyanosis in the patients of Hb M Saskatoon and Hb M Milwaukee-1 are discussed.
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A histidine-rich fragment, Cp F5, with a molecular weight of 18,650 was isolated from human ceruloplasmin. It consists of 159 amino acids and contains a possible copper-binding site. The sequence of the first 18 NH2-terminal residues of Cp F5 was determined by automated Edman degradation. ⋯ L. (1980) J. Biol. Chem. 255, 2886-2896), establish the complete amino acid sequence of Cp F5.