Chlorophyll a is a favorable substrate for Chlamydomonas Mg-dechelatase encoded by STAY-GREEN.
Mg removal from chlorophyll by Mg-dechelatase is the first step of chlorophyll degradation. Recent studies showed that in Arabidopsis, Stay Green (SGR) encodes Mg-dechelatase. Though the Escherichia coli expression system is advantageous for investigating the properties of Mg-dechelatase, Arabidopsis Mg-dechelatase is not successfully expressed in E. coli. Chlamydomonas reinhardtii SGR (CrSGR) has a long, hydrophilic tail, suggesting that active CrSGR can be expressed in E. coli. After the incubation of chlorophyll a with CrSGR expressed in E. coli, pheophytin a accumulated, indicating that active CrSGR was expressed in E. coli. Substrate specificity of CrSGR against chlorophyll b and an intermediate molecule of the chlorophyll b degradation pathway was examined. CrSGR exhibited no activity against chlorophyll b and low activity against 7-hydroxymethyl chlorophyll a, consistent with the fact that chlorophyll b is degraded only after conversion to chlorophyll a. CrSGR exhibited low activity against divinyl chlorophyll a and chlorophyll a', and no activity against chlorophyllide a, protochlorophyll a, chlorophyll c2, and Zn-chlorophyll a. These observations indicate that chlorophyll a is the most favorable substrate for CrSGR. When CrSGR was expressed in Arabidopsis cells, the chlorophyll content decreased, further confirming that SGR has Mg-dechelating activity in chloroplasts.
Institute of Low Temperature Science, Hokkaido University, N19 W8, Sapporo, 060-0819, Japan.
Kaori
K
Matsuda
Institute of Low Temperature Science, Hokkaido University, N19 W8, Sapporo, 060-0819, Japan.
Yousuke
Y
Shimoda
Institute of Low Temperature Science, Hokkaido University, N19 W8, Sapporo, 060-0819, Japan; CREST, Japan Science and Technology Agency, N19 W8, Sapporo, 060-0819, Japan.
Ayumi
A
Tanaka
Institute of Low Temperature Science, Hokkaido University, N19 W8, Sapporo, 060-0819, Japan; CREST, Japan Science and Technology Agency, N19 W8, Sapporo, 060-0819, Japan. Electronic address: ito98@lowtem.hokudai.ac.jp.
Hisashi
H
Ito
D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002696:Chlamydomonas / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D060365:Chloroplast Proteins; D004798:Enzymes / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D053858:Metabolic Networks and Pathways; D010802:Phylogeny; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013379:Substrate Specificity
D020418:Algal Proteins; D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D004798:Enzymes; D011994:Recombinant Proteins; C000594663:SGR2 protein, Arabidopsis; C421174:magnesium dechelatase; D002734:Chlorophyll; D000077194:Chlorophyll A
Chlamydomonas; Mg-dechelatase; Stay green; Substrate specificity