| Popis: |
Chloroplasts of Euglena gracilis var. bacillaris lack sulfate-activating enzymes. A mutant lacking chloroplasts and proplastids (W10BSmL) lacks the sulfolipid, indicating that sulfolipid accumulation is associated with the presence of plastids. Mitochondria or chloroplasts from Euglena incubated alone with 35SO42− and ATP fail to incorporate label into sulfolipid, but the two organelles incubated together under the same conditions accumulate labeled sulfolipid in the chloroplasts. Euglena chloroplasts alone incubated with [35S]cysteine form labeled sulfolipid. If Euglena mitochondria are incubated with 35SO42− and ATP and the mitochondria are removed by centrifugation, incubation of the supernatant fluid with Euglena chloroplasts results in labeling of the sulfolipid. The compound(s) responsible that pass from mitochondria to plastids appear to be sulfite, and to a lesser extent, cysteine. In agreement with this, incubation of Euglena chloroplasts alone with [35S]sulfite results in labeling of the sulfolipid; incubation with [35S]cysteine is less effective. Two new inhibitors of sulfolipid labeling in Euglena were identified in the present work, S-sulfocysteine and cysteine sulfinic acid. Both are effective in blocking the further conversion of labeled adenosine 5′-phosphosulfate (AP35S) to labeled reduced products in Euglena mitochondria; they were also effective in blocking sulfolipid labeling from 35SO42− in spinach chloroplasts. |
