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| Helicases are enzymes that bind to double stranded DNA. The helicase activity is to unwind and seperate the two strands for the purposes of replication, transcription, recombination, and DNA repair. All organisms, eukaryotic and prokaryotic, use helicases in one form or another. Viral and bacterial helicases are the most commonly studied types of helicases in current research because of their abundance and efficiency. For this reason, the focus of this paper will be on them.
There are many types of viruses and bacterium existing in the world today and each type has it's own variation of helicase. Most helicases have a similar structure when active, a double ring that is fomed by the dimerization of two nearly identical hexameric rings. This conformation usually requires Mg2+, ATP, or single stranded DNA to occur. Viral and bacterial DNA is circular and contains only one replication origin. This means that only two helicases are required to replicate the entire DNA genome. From the replication origin, the helicases follow the DNA strand in opposite directions until they meet on the opposite side. Feel free to explore the animations in this site by clicking and dragging on them. To zoom in or out, Hold down the "shift" key while dragging down or up on the picture. To see this animation again, click this button |