The Journal of biological chemistry
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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.