Structure of the Bradyrhizobium japonicum gene hemA encoding 5-aminolevulinic acid synthase.

The nucleotide (nt) sequence of the hemA gene, which encodes 5-aminolevulinic acid synthase (ALAS) from the bacterium Bradyrhizobium japonicum, is presented. This sequence predicts a protein of 408 amino acids (aa) with an Mr of 44,599. This predicted amino acid sequence is highly homologous to that of the chicken embryonic liver ALAS, exhibiting a 48.8% identical amino acid sequence over the entire length of the bacterial protein. A single mRNA start point was demonstrated by S1 protection analysis for the B. japonicum hemA. The 5' end of the transcript is 100 nt upstream from the start codon. The sequence of the promoter region has some sequence homology to the -35 nt region of the Escherichia coli consensus promoter sequence but not to the -10 nt region. There is also one block of 9 nt found in both the B. japonicum glnA and hemA promoter regions.