A NOVEL ENVIRONMENTALLY-REGULATED 33 KDA PROTEIN FROM TROPICAL AND TEMPERATE CNIDARIAN ZOOXANTHELLAE

1. A new technique was developed to extract soluble proteins from the intracellular dinoflagellate symbionts (zooxanthellae) of cnidarians, suitable for analysis by denaturing gel electrophoresis (SDS-PAGE). 2. Using this technique, a highly abundant 33 kDa protein has been detec ted from the zooxanthellae of both a temperate sea anemone (Anemonia v iridis) and three tropical corals (Goniopora djiboutiensis, G. pandora ensis and G. stokesi).3. Relative abundance of the protein varies with thermal shock, season, habitat from which the specimens were collecte d and laboratory holding conditions. 4. Amino acid sequence analyses a nd searches of current CD-ROM databases failed to find a significant m atch for a 31 residue amino-terminus sequence or an 8 residue internal sequence, but showed a partial (9 residue) homology with the vertebra te ''high-mobility group'' (HMG) nuclear proteins which are involved w ith DNA binding and unwinding during replication. We are currently see king funds to further investigate this apparently novel protein, with a view to assessing its potential role as an indicator of environmenta l stress in cnidarian zooxanthellae.