Prediction of terminal protein and ribonuclease H domains in the gene P product of hepadnaviruses

By means of comparative analysis of primary and secondary structures, and hydropathy plots of hepadnavirus P proteins new functional domains were revealed additionally to the polymerase domain which had been found earlier in these proteins. The C-terminal part of P proteins was revealed to be significantly similar to ribonuclease H of E. coli. The ribonuclease H functional domain is known to be an integral entity of retrovirus reverse transcriptase as a rule. Availability of this domain indicates once more the putative reverse transcriptase properties of the P products. The proteins of hepadnaviruses were compared to terminal proteins of picornaviruses, adenoviruses and bacteriophages. The data obtained suggested that a conservative N-terminal region of P proteins functions as protein primer for DNA synthesis in hepadnaviruses.