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The C. reinhardtii CF 1 with the mutation βT168S has high ATPase activity
Author(s) -
Hu Dongli,
Strotmann Heinrich,
Shavit Noun,
Leu Stefan
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)01531-7
Subject(s) - chlamydomonas reinhardtii , mutant , wild type , chloroplast , mutagenesis , atpase , biochemistry , chlamydomonas , enzyme , enzyme assay , atp synthase , biology , chemistry , microbiology and biotechnology , gene
We have generated the mutation T168S in the β subunit of the chloroplast ATP synthase complex of Chlamydomonas reinhardtii by site directed mutagenesis and chloroplast transformation. CF 1 and the α 3 β 3 γ complex of this mutant strain were isolated and their enzymatic activities were characterized and compared to those of the corresponding wild type complexes. Without activation the mutant CF 1 exhibits MgATPase activity with at least 10 times higher rates than the wild type enzyme. The MgATPase activity could be stimulated to some extent by methanol, but less by ethanol and octylglucoside. The α 3 β 3 γ complex had an even higher MgATPase activity, which was only slightly enhanced by ethanol or methanol. The ATPase activities of the mutant complexes, like those of the wild type complexes, displayed a sharp concentration optimum for Mg 2+ . Free ADP inhibited neither the mutant nor the wild type ATPase significantly. Azide, which strongly inhibited the ATPase activity of the wild type enzyme, inhibited the mutant enzyme only at an about 30 times higher concentration suggesting that the mutation T168S prevents trapping of a tightly bound MgADP by a catalytic site that regulates chloroplast ATPase activity. The mutant cells grew photoautotrophically at a growth rate of about 50%. Similar to the wild type the cells survived on minimal medium in the dark. Under heterotrophic conditions with acetate as energy and carbon source the mutant cells grew much faster than the wild type cells, but the chlorophyll content per cell decreased dramatically.