Change of functional site location in homologs: BPTI-like family. General placement of functional site is usually conserved in homologs, in particular, if their function remains the same. Serine protease inhibitors in the BPTI-like family in an example of a rare exception to this rule. Bovine pancreatic trypsin inhibitor (BPTI; pdb|1bth, chain P) and factor Xa inhibitor (also called TAP or tick anticoagulant protein; pdb|1d0d, chain A) perform the same function using different parts of the protein fold. Other BPTI-like family members utilize the same region of the protein to perform different functions: the N-terminal residues are the key functional residues of TAP (pdb|1d0d; chain A) and green mamba snake α-dendrotoxin (pdb|1dtx). Functional sites are indicated in purple in the MOLSCRIPT diagrams and with asterisks in the alignment.