AMINO-ACID-SEQUENCES OF THE ALPHA-SUBUNIT AND BETA-SUBUNIT OF HEMERYTHRIN FROM LINGULA-REEVII

The complete amino-acid sequences of the alpha- and beta-subunits of h emerythrin from the brachiopod Lingula reevii have been determined. Th ese subunits are found in equal proportions in coelomic hemerythrocyte s and form an octamer, presumably with an alpha(4) beta(4) composition . Both subunits were found to consist of 117 residues and to show 65% sequence identity to each other. Sequences of the alpha- and beta-subu nits of L. reevii hemerythrin are closely related to their counterpart s in hemerythrin from the related brachiopod, Lingula unguis, showing 95% and 87% sequence identities, respectively. Sequence alignments sho w that 25 residues in the lingulid hemerythrin subunits are identical to those found in other hemerythrins and myohemerythrins. These conser ved residues include those known to provide iron ligands. However, the se comparisons also indicate that the lingulid hemerythrin sequences a re distinct from those of the sipunculid and annelid hemerythrins and myohemerythrins.