Reverse transcriptase biological roles

Subsequently, a protein component of telomerases also was identified. From its amino acid sequence, this component is clearly related to reverse transcriptases, enzymes first discovered in retroviruses that copy RNA into DNA. Thus, telomerase is a specialized reverse transcriptase that carries its own template. Telomeres may play important roles in cancer-cell biology and in cell aging. 

The biological applications of manganese are numerous and quite varied. Although most of these biological roles utilize manganese in structural or hydrolytic systems, some very striking redox systems are also known. The hydrolytic roles are, of course, not to be overlooked with respect to the widespread and critical arginase enzyme, which exhibits a strict requirement for two Mn" ions. The ribo-nuclease hydrolases of retroviral reverse transcriptase are another key nonredox application—for example, the ribonuclease hydrolase from HIV-1. 

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