Biopolymers from marine invertebrates. XIII. Characterization of an antibacterial protein, dolabellanin A, from the albumen gland of the sea hare, Dolabella auricularia

An antibacterial factor, dolabellanin A, was purified from the albumen gland of a sea hare, Dolabella auricularia. Purified dolabellanin A was a glycoprotein of 250 kilodaltons consisting of 4 subunits, and showed both antibacterial and antineoplastic activities. The two activities were lost in parallel on heating and at low and high pH. This factor was half-maximally active for gram-positive and -negative bacteria at 0.018-0.48 microgram/ml, and its action was not bactericidal but bacteriostatic. Dolabellanin A did not induce morphological elongation of bacteria or the release of adenosine triphosphate, but it completely inhibited the syntheses of deoxyribonucleic acid (DNA) and ribonucleic acid by E. coli within 6 min. These results suggest that dolabellanin A, which is found in a marine invertebrate, the sea hare, is a new antibacterial protein, and that it exerts its action by inhibiting nucleic acid synthesis, as does a DNA-inhibiting chemotherapeutic drug.