Single Strand Binding Protein

∞ generated and posted on 2016.12.04 ∞

Means by which cells prevent DNA that has been opened at the replication fork during DNA replication from immediately reestablishing the pre-opening double helix conformation.

A Single-Strand Binding Protein literally is a protein that binds to an isolated half of a double helix, usually only temporarily isolated as in the course of DNA replication and in order to keep that DNA strand temporarily isolated from its complementary strand.

DNA is most stable under physiological conditions when existing within a double helix, so long as complementary strands of DNA are present in the same location. After the enzyme called helicase separates the double helix into individual, single strands of DNA, then those strands thus will tend to reform the double helix unless they are prevented from doing so.

Single-strand binding protein is attached to these post-replication fork single strands of DNA, preventing their "reannealing" that is, reforming the double-stranded, double helix state.

DNA that has been converted from a double-stranded form to a single-stranded form can be said to have been denatured. What single-strand binding protein does is to prevent this denatured DNA from renaturing, either between the two DNA strands that are being replicated or within an individual strand that is being replicated (with the latter a concern especially with the lagging strand).

Once the daughter strand has been synthesized, then the double helix has been reestablished without this renaturation occurring, thus eliminating the need to for single-strand binding protein as the DNA is no longer single stranded. The job of single-strand binding protein thus is to prevent renaturation of DNA just long enough so that DNA replication can occur, after which single-strand binding protein is no longer needed (for that particular length of now-replicated DNA).

Also known as single-stranded binding protein. Note that there are plenty of proteins which bind to double-stranded DNA, though they don't tend to be described as such since that's pretty much the typical situation.