THE PRIMARY STRUCTURE OF SOYBEAN LEGHEMOGLOBIN

Abstract

This chapter focuses on primary structure of soybean leghemoglobin. Leghemoglobin is the only hemoglobin-like protein found in the plant kingdom. Leghemoglobin can be resolved by electrophoresis and ion exchange chromatography on DEAE cellulose into two main components of molecular weight about 17,000, each containing one heme group per molecule. The hydrolysis of the apoprotein by trypsin, chymotrypsin, and thermolysin, purification of the peptide fragments on Dowex and Dowex or by high-voltage electrophoresis and determination of the amino-acid sequences of these peptides have been described. The most striking feature of Lba is the complete absence of sulfur-containing amino acids. Another characteristic is that it contains only one pair of histidine residues, which is the minimum number expected if they are assumed to be the heme-binding residues identical to those found in vertebrate hemoglobins. Leghemoglobin differs from vertebrate hemoglobins by having no basic center. The polypeptide chains of hemoglobin and myoglobin usually have one heme-binding histidine residue in the middle, in contrast to cytochrome c.