Chloroplast ATPase in A cetabularia acetabulum : Purification and Characterization of Chloroplast F_1-ATPase

概要

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ATPases were isolated from chloroplasts of the unicellular marine alga Acetabularia acetabulum. Two preparations of ATPase, a chloroplast-enriched fraction and an αβγ-complex were compared. The αβγ-complex was released into an EDTA solution and purified by anion-exchange chromatography, hydrophobic chromatography, and gel permeation chromatography. The subunit composition of this enzyme appeared to be 52-53(α), 51(β), and 40(γ)kDa from SDS-PAGE. ATPase activity was enriched about 260-fold to a specific activity of approximate 4. 1 U・mg protein ^<-1>. The catalytic properties of the αβγ-complex were as follows : pH optimum at 7. 5 ; substrate specificity, ATP > ITP, GTP > UTP = CTP (K_m for ATP 0. 2 mM) ; divalent cation requirement, Mg^<2+> = Mn<2+> = Co^<2+> > Zn^<2+> > Ni^<2+> > Ca^<2+> ; ATPase activity was inhibited by monovalent anions (NO^-_3, SCN^-), while monovalent cations had neither inhibitory nor stimulatory effects. Orthovanadate had no inhibitory effect on the enzyme activity of αβγ-complex. Azide was the most effective inhibitor of the αβγ-complex. N-Terminal amino acid sequences of the α and βsubunits were not obtained and appeared to be blocked. The γ subunit gave a sequence of AGLKEMKD-XIGSVXNTKKI, which showed 60% similarity to the γ subunits of spinach and Chlamydomonas reinhardtii CF_1-ATPase and EF_1-ATPase.
社団法人日本農芸化学会の論文
1994-03-23