And although the proteins share only about 15 percent amino acid sequence identity overall, they're much more similar at the local level, particularly at the domain responsible for binding and cleaving GTP.
Why provide a number when it shows a difference and only a vague "much more" when the similarity is purported to be important? It seems to me that the number, if significant should be at least 30%, given my interpretation of much and the general chimp/human genome simularity of ~98%. (it also matters as to the definition of local)
It's very easy to count matching and non-matching amino acids. How do you quantify similarity of shape and structure?
I don't think they meant to quantify those attributes, rather I thought they meant the sequence of the proteins local to the active parts of the structure, the bonding sites for instance. At those critical points the sequence would be more sensitive to change and likely to be selected out/in.
Yes and no. When it comes to proteins that are as separated as those from bacteria and mammalian it can be difficult.
How do you quantify similarity of shape and structure?
I am not sure if this is a rhetorical question or not. If so what is your point? If not, I will address it.