What are invariant amino acids and where are they located?

I keep googling it but I cannot find any information just journal articles

Thank you for using the Jiskha Homework Help Forum. Since we don't know which links you have tried, here are some thay may help you:

1. http://www.ingentaconnect.com/content/oup/nar/2005/00000033/00000019/art06418

2. http://nar.oxfordjournals.org/cgi/content/abstract/33/19/6418

3. http://www.springerlink.com/content/p840152h37w487uj/