A conserved tryptophan (W91) at the barrel-lid junction modulates the packing and stability of Kunitz (STI) family of inhibitors

Roles of inter- and intramolecular tryptophan interactions in membrane-active proteins revealed by racemic protein crystallography

“…Indeed, the heterocyclic ring of tryptophan exhibits a wide spectrum of polarity that has been demonstrated to interact with various components of the lipid membrane domains 2 . It can associate with a cationic group such as choline through π-based interactions 3,4 , the hydrophobic alkyl chain of a fatty acid or amino acid [5][6][7] , or a H-bond acceptor such as the phosphate head group by donating the indole's N-H 8,9 . In line with the dynamical nature of proteins 10 , a tryptophan residue may have multiple interacting partners that interchange during the course of action 2 .…”