Abstract
Mg-chelatase catalyzes the insertion of Mg2+ into protoporphyrin IX and is composed of three subunits, CHLI, CHLD and CHLH. Mg-insertion requires ATP hydrolysis by CHLI, the primary determinants of the rate of Mg-insertion. Our previous study showed that thioredoxin (Trx) assists the DTT-dependent increase of ATPase activity of Arabidopsis CHLI1. Thorough analysis of the reduction of CHLI1 was carried out by using a combination of NADPH, NADPH-Trx reductase and Trx. Gel-shift analysis with SH-modifying reagent AMS and ATPase assay of CHLI1 confirmed the Trx-dependent redox regulation. Observation of the in vivo redox state of CHLI showed that CHLI exists as an oxidized form in the dark, while it is reduced in the light. To determine the critical cysteine for this redox-regulation, the analysis of the serine mutants of 4 cysteine residues of CHLI1 is currently underway.
