The Vast Structural Diversity of Antimicrobial Peptides

Antimicrobial peptides (AMPs) occur in all kingdoms of life and are integral to host defense. They have diverse structures and target a variety of organisms, both by nonspecific membrane interactions and via specific targets. Here we discuss the structures of AMPs from the four main classes currently recognized - that is, peptides with (i) α-helical, (ii) β-sheet, (iii) αβ, or (iv) non-αβ elements - as well as the growing pool of complex topologies including various post-translational modifications (PTMs). We propose to group these latter peptides into a fifth class of AMPs. Such peptides exhibit high stability and amenability to chemical engineering, making them of interest for the development of novel antimicrobial agents. Advances and challenges in the development of these peptides towards therapeutic leads are presented.