Reverse transcriptase

Reverse transcriptase plays a role in retrovirus replication. It catalyzes the synthesis of the DNA strand complementary to a given RNA template.

Naming: By convention viral polymerases are called RNA/DNA-dependent whereas cellular polymerases are called RNA/DNA-directed.

Priming:

RNA 3'OH (Retroviridae, LTR retrotransposons, Caulimoviridae, Hepadnaviridae)
DNA 3'OH (LINE, SINE)
RTase at Tyr-OH residue (Caulimoviridae, Hepadnaviridae)
a Guanosine 2'OH in retron mRNA (Retrons)

Enzymatic reaction:

DNA nucleotidyltransferase (RNA-dependent) EC:2.7.7.49 RHEA:22508

Mechanism Viral Rtase are characterized by a conserved motif in which two conserved aspartic acid residues are bound to two magnesium ions. The reaction begins with the deprotonation of primer's 3' OH, in a manner that doesn't require a base . Subsequently, the 3'-oxygen acts as a nucleophile to attack the phosphate bond and eventually releases a pyrophosphate.