Enzyme responsible for opening the replication fork for DNA replication.
Helicase is called helicase because, by unwinding the double helix, the twist of the helix that is removed in one direction (towards the newly synthesized DNA) is imposed on the DNA that is upstream from the replication fork (i.e., in the direction the replication fork is traveling).
The result is called supercoiling, a super twisting of the upstream DNA. The excess twisting is subsequently relieved by another enzyme, called DNA gyrase.
Following the opening of the replication for by helicase, the newly exposed single strands of DNA are unstable in the sense that they would prefer to reform back into a double helix. That tendency is blocked, however, by the binding of single-strand binding protein to these now exposed single strands of DNA.
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