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

Technical Report · Thu Dec 31 04:00:00 EST 1992

DOI:https://doi.org/10.2172/10158546· OSTI ID:10158546

Soell, D

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 {yields} 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 T{Psi}C-loop. The altered tRNA supports protein but not ALA synthesis.

• Research Organization: Yale Univ., New Haven, CT (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-87ER13734
• OSTI ID: 10158546
• Report Number(s): DOE/ER/13734--4; ON: DE93014398
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505
550200
59 BASIC BIOLOGICAL SCIENCES
ALGAE
ARABIDOPSIS
BIOCHEMISTRY
BIOLOGICAL PATHWAYS
CHLOROPLASTS
DNA-CLONING
ESCHERICHIA COLI
FRACTIONATION
GLUTAMIC ACID
ISOMERASES
NUCLEOTIDE DEHYDROGENASES
PHOTOCHEMICAL, PHOTOBIOLOGICAL, AND THERMOCHEMICAL CONVERSION
PROGRESS REPORT
TRANSFER RNA