Protein Structure Similarity

Since a protein’s amino acid sequence determines 3D structure, which in turn determines protein function, one might think that sequence similarity is also very good predictor of functional similarity, but this turns out to be less the case than with structural similarity. Vastly different amino acid sequences can yield very different structures, and similar sequences can sometimes yield dissimilar structures. Thus, sequence similarity is a far less reliable predictor of functional similarity than structural similarity is.