Structural Studies of Histidine Decarboxylase from Micrococcus SP. N.

This is the authors' abstract. We don't add key points for this paper.

The isolated small and large subunits of carboxymethylated histidine decarboxylase from Micrococcus sp. n. as well as the purified tryptic peptides from each protein chain were analyzed for amino acid sequence. In the small subunit the positions of all four methionine residues were characterized, both terminal regions were identified and over half of the entire structure was determined. All peptides containing methionine in the large subunit were also identified. The N-terminus of this unit is blocked by a pyruvic acid residue. This was converted to alanine by reductive amination, which permitted direct sequential degradation of the large subunit also. The peptides containing carboxymethylcysteine derive exclusively from the large subunit and form two pairs of overlapping fragments, corresponding to only two unique cysteine residues in the whole protein. The results establish a complete dissimilarity between the subunits, and are a requirement for a determination of the entire primary structure of the protein by cleavage with cyanogen bromide.