[The first steps of chlorophyll synthesis: RNA involvement and regulation]

Technical Report · Wed Jan 01 04:00:00 EST 1992

DOI:https://doi.org/10.2172/6528189· OSTI ID:6528189

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: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-87ER13734
• OSTI ID: 6528189
• Report Number(s): DOE/ER/13734-4; ON: DE93014398
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ALGAE
AMINO ACIDS
ARABIDOPSIS
BACTERIA
BIOLOGICAL PATHWAYS
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHLOROPLASTS
CLONING
DNA HYBRIDIZATION
DNA-CLONING
DOCUMENT TYPES
ENZYMES
ESCHERICHIA COLI
FRACTIONATION
GLUTAMIC ACID
HYBRIDIZATION
ISOMERASES
MAGNOLIOPHYTA
MAGNOLIOPSIDA
MICROORGANISMS
NUCLEIC ACIDS
NUCLEOTIDE DEHYDROGENASES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PLANTS
PROGRESS REPORT
PROTEINS
RNA
SEPARATION PROCESSES
TRANSFER RNA