Amino acid composition and relationships of lupin and serradella leghaemoglobins.

The amino acid compositions of two lupin and two serradella leghaemoglobins were determined by conventional techniques. They are as follows: Lupin component I: Ala20, Arg1, (Asp + Asn)17, (Glu + Gln)17, Gly9, His4, Ile9, Leu15, Lys17, Met1, Phe8, Pro5, Ser12, Thr9, Trp3, Tyr2 and Val17. Lupin component II: Ala26, Arg1, (Asp + Asn)18, (Glu + Gln)20, Gly9, His5, Ile10, Leu16, Lys18, Met1, Phe8, Pro6, Ser12, Thr10, Trp3, Tyr2 and Val18. Serradella component I: Ala32, Arg1, (Asp + Asn)10, (Glu + Gln)18, Gly8, His3, Ile5, Leu5, Lys13, Phe8, Pro4, Ser14, Thr7, Try2, Tyr3 and Val12. Serradella component II: Ala37, Arg1, (Asp + Asn)11, (Glu + Gln)20, Gly9, His3, Ile6, Leu17, Lys15, Phe9, Pro5, Ser16, Thr8, Try2, Tyr3 and Val13. Notable features of these are (a) the absence of cyst(e)ine, which suggests that each is a single polypeptide chain (b) the presence of a methionine residue in the lupin leghaemoglobins, and (c) the high contents of alanine, aspartic acid plus asparagine, glutamic acid plus glutamine, leucine, lysine, serine and valine. The relationships of leghaemoglobins to each other and to other groups of haem-containing proteins have been investigated using a statistical procedure based on amino acid composition.