Isolation and identification of paramyosin from amphioxus notochord

Paramyosin was extracted and purified from the notochordal lamellae of the amphioxus, Branchiostoma lanceolatum. The subunit molecular weight, as determined by dodecyl sulphate gel electrophoresis, was 108 000. The amino acid composition of amphioxus paramyosin, although similar to that of invertebrate paramyosin, showed differences: a higher content of proline, a lower amount of dicarboxylic amino acids, and a lysine/arginine ratio greater than one. Electron microscopy of paracrystals formed by divalent cations showed the axial periodicities of 144 or 725 A and the subperiod of 48 A, which is specific for paramyosin. The fine structure of amphioxus paracrystals differed from that of molluscan paramyosin.