Two types of ferrochelatase in photosynthetic and nonphotosynthetic tissues of cucumber: their difference in phylogeny, gene expression, and localization.
Ferrochelatase catalyzes the insertion of Fe(2+) into protoporphyrin IX to generate protoheme. In higher plants, there is evidence for two isoforms of this enzyme that fulfill different roles. Here, we describe the isolation of a second ferrochelatase cDNA from cucumber (CsFeC2) that was less similar to a previously isolated isoform (CsFeC1) than it was to some ferrochelatases from other higher plants. In in vitro import experiments, the two cucumber isoforms showed characteristics similar to their respective ferrochelatase counterparts of Arabidopsis thaliana. The C-terminal region of CsFeC2 but not CsFeC1 contained a conserved motif found in light-harvesting chlorophyll proteins, and CsFeC2 belonged to a phylogenetic group of plant ferrochelatases containing this conserved motif. We demonstrate that CsFeC2 was localized predominantly in thylakoid membranes as an intrinsic protein, and forming complexes probably with the C-terminal conserved motif, but a minor portion was also detected in envelope membranes. CsFeC2 mRNA was detected in all tissues and was light-responsive in cotyledons, whereas CsFeC1 mRNA was detected in nonphotosynthetic tissues and was not light-responsive. Interestingly, tissue-, light-, and cycloheximide-dependent expressions of the two isoforms of ferrochelatase were similar to those of two glutamyl-tRNA reductase isoforms involved in the early step of tetrapyrrole biosynthesis, suggesting the existence of distinctly controlled tetrapyrrole biosynthetic pathways in photosynthetic and nonphotosynthetic tissues.
Suzuki
Takuo
T
Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8501 Japan.
Masuda
Tatsuru
T
Singh
Davinder Pal
DP
Tan
Fui-Ching
FC
Tsuchiya
Tohru
T
Shimada
Hiroshi
H
Ohta
Hiroyuki
H
Smith
Alison G
AG
Takamiya
Ken-ichiro
K
D000445:Aldehyde Oxidoreductases / Q000737:chemistry; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology; D015152:Blotting, Northern; D015153:Blotting, Western; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018553:Cucumis sativus / Q000201:enzymology; D003513:Cycloheximide / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005294:Ferrochelatase / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D018532:Pisum sativum; D010788:Photosynthesis; D010802:Phylogeny; D020033:Protein Isoforms; D011498:Protein Precursors / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D013347:Subcellular Fractions; D020524:Thylakoids / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution
D018076:DNA, Complementary; D020033:Protein Isoforms; D011498:Protein Precursors; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D003513:Cycloheximide; D000445:Aldehyde Oxidoreductases; C067282:glutamyl tRNA reductase; D005982:Glutathione Transferase; D005294:Ferrochelatase