Figure 5.

Nucleotide sequence conservation of the pol I catalytic site within individual genus. Most prokaryote and eubacteria polA genes sequenced retain the DYSQIELR motif A sequence; however, a few organisms, including those in the Mycobacterium genus, contain amino acid substitutions (e.g., Leu → Met). To further characterize the apparently slow evolution of the polymerase active site, nucleotide sequences obtained from GenBank blast searches were compared. These results show nearly 0% base sequence change of motif A residues within each genus. Outside of motif A, 10–50% of identical amino acids at specific loci are encoded by alternate codons. Universal codons from the DNA (+) strand encoding for motif A amino acids are shown on Top.