Electrophoretic characterization of nuclear basic proteins in the toxic marine dinoflagellate Gymnodinium mikimotoi

Abstract

Gymnodinium mikimotoi is a toxic unicellular marine dinoflagellate that frequently forms red tide blooms in both the northern Atlantic and northern Pacific Oceans. G. mikimotoi was chosen as a study organism because of its high growth rate and its relatively fragile cell wall in comparison to other dinoflagellates. Dinoflagellates do not have histones, possessing instead one to several nuclear basic proteins, which play an unknown role in the dinoflagellate nucleus. Characterization of these histone-like proteins, will further elucidate their role. Only one acid extractable protein was seen in one-dimensional SDS-PAGE, which showed a V8 protease digestion pattern similar to that of HCc. When the nuclear acid extract was run on AU-PAGE and AUT-PAGE, two and four bands were seen, respectively. It was determined that G. mikimotoi has four HGm variants, named α1, α2, β, and γ. Through peptide mapping, variants β and γ were seen to be similar, as were α1 and α2. Acidic native APGE showed possible oxidized protein spots, consistent with those seen previously in Crypthecodinium cohnii. HGm variants responded to nitrogen stress and time of day, but did not respond to other environmental variations. Therefore, while the protein was further characterized, its function remained elusive.