[The first steps of chlorophyll synthesis [electronic resource] : RNA involvement and regulation]. Progress report, January 1990--June 1992

Published:: Washington, D.C. : United States. Dept. of Energy, 1992.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description:: 5 pages : digital, PDF file
Additional Creators:: Yale University, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information

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Summary:

Glu-tRNA{sup Glu} is synthesized from glutamate and tRNA{sup Glu} by glutamyl-tRNA synthetase (GluRS). Recent work has demonstrated that Glu-tRNA{sup Glu} has dual functions and is a precursor for protein and 5-aminolevulinate (ALA) synthesis. Current data does not provide compelling evidence for the notion that GluRS is regulated by chlorophyll precursors or in concert with the other enzymes of ALA synthesis. We have redefined the C5-pathway as a two-step route to ALA starting with Glu-tRNA{sup Glu}. Only two enzymes, Glu-tRNA reductase (GluTR) and GSA-2,1-amino-mutase (GSA-AM), are specifically involved in ALA synthesis. We have purified these enzymatic activities from Chlamydomonas and demonstrated that the two purified proteins in the presence of their cofactors NADPH and pyridoxal phosphate are sufficient for the in vitro Glu-tRNA → ALA conversion. We have cloned the genes encoding GluTR. The sequences of the GluTR proteins deduced from these genes share highly conserved regions with those of bacterial origin. We havealso cloned and analyzed the gene encoding GSA-AM from Arabidopsis. As in Salmonella typhimurium, there are indications of the existence of an additional pathway for ALA formation in E. coli. To shed light on the recognition of the single tRNA{sup Glu} by the chloroplast enzymes GluTR, GluRS we characterized a chlorophyll-deficient mutant of Euglena having tRNA{sup Glu} with a point mutation in the TΨC-loop. The altered tRNA supports protein but not ALA synthesis.

Report Numbers:

E 1.99:doe/er/13734--4
doe/er/13734--4

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Note:

Published through SciTech Connect.
12/31/1992.
"doe/er/13734--4"
"DE93014398"
Soell, D.

Type of Report and Period Covered Note:

Annual; 01/01/1991 - 12/31/1992

Funding Information:

FG02-87ER13734

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