The amino acid sequence of pea (Pisum sativum) leghemoglobin

The amino acid sequence has been determined for leghemoglobin component I from root nodules of pea, Pisum sativum. Pea leghemoglobin is one polypeptide chain composed of 147 amino acids, it contains one methionine residue at position 144, and three histidines, which are at positions 60, 92 and 101. The sequence has at least seven polymorphic residues, but it was not possible to separate the polymorphic protein forms which had identical electric charge. The approximate molecular weight of pea leghemoglobin component I is 16,350. The other major leghemoglobin component (II) from pea has an amino acid composition very similar to that of leghemoglobin component I, suggesting that the gene has duplicated relatively recently. P. sativum leghemoglobin differs from that of Vicia faba by 22--23%, depending on the polymorphic form. The leghemoglobins from Phaseolus vulgaris and Glycine max differ from pea leghemoglobin by 35--44%, and Lupinus luteus leghemoglobins differ from it by 45--48%. The seven leghemoglobins so far sequenced have 50 residues (33%) which are common to all.