Primary structural comparison of RNA-dependent polymerases from plant, animal and bacterial viruses

Possible alignments for portions of the genomic codons in eight different plant and animal viruses are presented: tobacco mosaic, brome mosaic, alfalfa mosaic, sindbis, foot-and-mouth disease, polio, encephalomyocarditis, and cowpea mosaic viruses. Since in one of the viruses (polio) the aligned sequence has been identified as an RNA-dependent polymerase, this would imply the identification of the polymerases in the other viruses. A conserved fourteen-residue segment consisting of an Asp-Asp sequence flanked by hydrophobic residues has also been found in retroviral reverse transcriptases, a bacteriophage, influenza virus, cauliflower mosaic virus and hepatitis B virus, suggesting this span as a possible active site or nucleic acid recognition region for the polymerases. Evolutionary implications are discussed.