 Turns can also be found in different parts of the protein, for instance, joining the β-strands.There are surface residues which actively participate in the active site of AcrF1, two of which are tyrosines (Y6 and Y20) and the third amino acid is a glutamic acid (E31), as their mutation by an alanine causes a 100-fold decrease in the activity of the protein (with Y20A and E31A mutations), and a 107-fold decrease when Y6 is mutated.The different structures that form the protein create a strange combination, as Maxwell et al.