In this video, we're going to talk about some of the enzymes and proteins involved with the unwinding of the DNA during DNA replication, and these include the enzymes topoisomerase and helicase, as well as the protein single stranded binding proteins or SSBs. Several different proteins participate in the unwinding of the DNA during DNA replication. Of course, the unwinding of the DNA refers to the separation of the two strands of DNA. These include the proteins, these three proteins that are listed down below, 1, 2, and 3, and the first of these three is topoisomerase, which is also sometimes referred to as DNA gyrase in prokaryotes. Topoisomerase, or DNA gyrase, functions to cut and rejoin the DNA to relieve strain caused by DNA supercoiling. DNA supercoiling can actually inhibit DNA replication and therefore must be relieved in order for DNA replication to proceed normally.
If we take a look at our image below, over here on the left, we're showing you some DNA supercoiling. You can see that we're showing you a DNA molecule, but the DNA molecule here is supercoiling, and this structure that you see here is a DNA supercoil. The DNA supercoil is going to cause strain and can inhibit DNA replication, and this DNA supercoil must be relieved in order for DNA replication to proceed, and that is the function of the DNA gyrase or the topoisomerase, which is right here ahead of the replication fork. The DNA gyrase's job is to eliminate or remove the DNA supercoils. The supercoiling can be better understood by comparing it to the supercoiling of old telephone wires, which supercoil just like the DNA molecule tends to supercoil. Topoisomerase helps with getting rid of and eliminating the DNA supercoils.
The second protein involved in the unwinding of the DNA is helicase, which unwinds the DNA by breaking hydrogen bonds. The hydrogen bonds form between the two DNA strands. When helicase breaks these hydrogen bonds between the two strands, it separates them. Helicase helps to create single stranded DNA. If we take a look at our image below, you will notice that helicase is represented as this yellow triangle and its job is to break the hydrogen bonds that hold the two DNA strands together, separating the two DNA strands, creating single stranded DNA. The third proteins that come into play are the single stranded binding proteins, which are abbreviated as just SSBs. These single stranded binding proteins, or SSBs, bind to the single stranded DNA to prevent the reannealing of the DNA, to prevent those hydrogen bonds from reforming, and they also prevent the degradation of each of these single stranded DNA molecules since single stranded DNA within cells tends to be degraded.
When we take a look at our image down below, notice that the single stranded binding proteins are these orange circles here that are binding to the single stranded DNA that's being separated here. These are the proteins that are going to be important for the unwinding of the DNA and the separation of the two strands of DNA so that they can serve as templates for building the brand new DNA strands. This here concludes our lesson on the unwinding of the DNA, and we'll be able to do some practice applying the concepts that we've talked about here as we move forward in our course. So I'll see you all in our next video.