Identification of the enzymatic basis for delta-aminolevulinic acid auxotrophy in a hemA mutant of Escherichia coli.
The hemA mutation of Escherichia coli K-12 confers a requirement for delta-aminolevulinic acid (ALA). Cell extract prepared from the hemA strain SASX41B was incapable of producing ALA from either glutamate or glutamyl-tRNA, whereas extract of the hem+ strain HB101 formed colorimetrically detectable amounts of ALA and transferred label from 1-[14C]glutamate and 3,4-[3H]glutamyl-tRNA to ALA. Extracts of both strains converted glutamate-1-semialdehyde to ALA and were capable of aminoacylating tRNAGlu. Glutamyl-tRNA formed by extracts of both strains could be converted to ALA by the extract of hem+ cells. The extract of hemA cells did not convert glutamyl-tRNA formed by either strain to ALA. However, the hemA cell extract, when supplemented in vitro with glutamyl-tRNA dehydrogenase isolated from Chlorella vulgaris cells, formed about as much ALA as did the unsupplemented hem+ cell extract. We conclude from these observations that the enzyme activity that is lacking in the ALA auxotrophic strain carrying the hemA mutation is that of glutamyl-tRNA dehydrogenase.
Avissar
Y J
YJ
Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912.
Beale
S I
SI
D000622:Aminolevulinic Acid / Q000096:biosynthesis*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005971:Glutamates / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D007658:Ketone Oxidoreductases / Q000378:metabolism*; D007982:Levulinic Acids / Q000096:biosynthesis*; D009154:Mutation; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism
D005971:Glutamates; D007982:Levulinic Acids; D012346:RNA, Transfer, Amino Acyl; D000622:Aminolevulinic Acid; D007658:Ketone Oxidoreductases; C059846:glutamyl tRNA dehydrogenase; D005998:Glycine