Characterization of CF₁ from the Diatom <i>Odontella sinensis</i>

Abstract

Abstract The CF 1 moiety of the chloroplast ATPase of the diatom Odontella sinensis was solubilized from isolated thylakoids by chloroform extraction. Further purification was achieved by HPLC on a Superose‐6 column. The resulting four‐subunit complex was identified as CF 1 lacking subunit δ. The larger two subunits, α and β, showed cross‐reactivity with antisera raised against the homologous subunits of spinach‐CF 1 . Western blot analysis further revealed that — contrary to other ATPases — migration in SDS‐PAGE of α was faster than migration of β, suggesting a deletion of 40 to 50 amino acids in subunit α of Odontella . The assumed deletion does not involve the N‐terminal side of the protein, as was established by protein sequencing. The N‐terminal sequences of subunits α and γ showed highest homologies with the equivalent subunits of blue‐green algae. According to SDS‐PAGE, the apparent molecular weights of the four Odontella subunits were 53.2 (β), 51.2 (α), 39.3 (γ) and 16.2 (ε) kD. ATPase activity of isolated Odontella ‐CF 1 could be induced by trypsin or octylglucoside, and to a lesser extent by sulfite or by alcohols such as methanol or ethanol.