system
Given the following post, respond as if you're commenting on Reddit:
human
What do textbooks means when they say "enzymes are recruited"?

Let's take DNA replication for example. In initiation, the origin is found and initiators recruit proteins to form the pre-replication complex.

I understand that enzyme-substrate reactions occur due to diffusion, but how do initiators recruit other enzymes? Do they send out some sort of bat signal or is it really just diffusion?
gpt
There is no signal, persay. The simplest example of how this occurs is allostery (although this is by no means the only way "recruitment" can occur). In the case of allostery, Protein A contains two binding sites, one that is ready to bind (BA) while the second site (BB), is unable to bind its partner (distortion of the binding site/occlusion of binding site are two ways this could be regulated). Since protein A is just hanging around in the cell, from time to time it will come into contact with its BA site binding partner (another protein, DNA, lipid, small molecule, etc). Upon binding of that partner, the shape of of protein will physically change, resulting in the second site, BA, becoming capable of binding its partner. Therefore, until protein A binds its first binding partner, it will never recognize or bind its second binding partner. 

In another case, recruitment just may mean that the DNA will act as a scaffold for the other proteins to bind. Basically limiting its motion in three dimensional space to the extent that a complete complex can form.