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A point mutation in Euglena gracilis chloroplast tRNA(Glu) uncouples protein and chlorophyll biosynthesis
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Stange-Thomann, N., Thomann, H. U., Lloyd, Adrian J., Lyman, H. and Söll, D. (1994) A point mutation in Euglena gracilis chloroplast tRNA(Glu) uncouples protein and chlorophyll biosynthesis. Proceedings of the National Academy of Sciences of the United States of America, 91 (17). pp. 7947-7951. doi:10.1073/pnas.91.17.7947 ISSN 0027-8424.
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Official URL: https://doi.org/10.1073/pnas.91.17.7947
Abstract
The universal precursor of tetrapyrrole pigments (e.g., chlorophylls and hemes) is 5-aminolevulinic acid (ALA), which in Euglena gracilis chloroplasts is derived via the two-step C5 pathway from glutamate charged to tRNA(Glu). The first enzyme in this pathway, Glu-tRNA reductase (GluTR) catalyzes the reduction of glutamyl-tRNA(Glu) (Glu-tRNA) to glutamate 1-semialdehyde (GSA) with the release of the uncharged tRNA(Glu). The second enzyme, GSA-2,1-aminomutase, converts GSA to ALA. tRNA(Glu) is a specific cofactor for the NADPH-dependent reduction by GluTR, an enzyme that recognizes the tRNA in a sequence-specific manner. This RNA is the normal tRNA(Glu), a dual-function molecule participating both in protein and in ALA and, hence, chlorophyll biosynthesis. A chlorophyll-deficient mutant of E. gracilis (Y9ZNalL) does not synthesize ALA from glutamate, although it contains GluTR and GSA-2,1-aminomutase activity. The tRNA(Glu) isolated from the mutant can still be acylated with glutamate in vitro and in vivo. Furthermore, it supports chloroplast protein synthesis; however, it is a poor substrate for GluTR. Sequence analysis of the tRNA and of its gene revealed a C56-->U mutation in the resulting gene product. C56 is therefore an important identity element for GluTR. Thus, a point mutation in the T loop of tRNA uncouples protein from chlorophyll biosynthesis.
| Item Type: | Journal Article | ||||||
|---|---|---|---|---|---|---|---|
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) | ||||||
| Journal or Publication Title: | Proceedings of the National Academy of Sciences of the United States of America | ||||||
| Publisher: | National Academy of Sciences | ||||||
| ISSN: | 0027-8424 | ||||||
| Official Date: | 16 August 1994 | ||||||
| Dates: |
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| Volume: | 91 | ||||||
| Number: | 17 | ||||||
| Page Range: | pp. 7947-7951 | ||||||
| DOI: | 10.1073/pnas.91.17.7947 | ||||||
| Status: | Peer Reviewed | ||||||
| Publication Status: | Published | ||||||
| Access rights to Published version: | Restricted or Subscription Access |
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