5-AMINOLEVULINIC ACID FORMATION IN ARABIDOPSIS-THALIANA

Glutamyl-tRNA (Glu-tRNA(Glu)) is a precursor used in protein and porph yrin biosynthesis in chloroplasts and many bacteria. Here we review th e current knowledge of tRNA(Glu) and the two enzymes, Glu-tRNA reducta se and GSA-2,1-aminomutase, which together with tRNA(Glu) form 5-amino levulinic acid (ALA). Using barley chloroplast tRNA(Glu) as a probe th e corresponding gene from Arabidopsis thaliana was isolated. This gene was located on a 1.1 kb EcoRI fragment in chloroplast DNA next to two genes encoding tRNA(Tyr) and tRNA(Asp). The tRNA(Glu) gene contains 7 3 nucleotides and differs from barley, rice and wheat chloroplast tRNA (Glu) in one base. The 3'-terminal CCA-end is not encoded. This tRNA w as expressed in Escherichia coli using the lpp promoter.