Peptides are amino acid chains that act as a messengers between cells and the body’s systems. They can modulate a wide range of cellular processes including hormones, growth factors and neurotransmitters. They are used in everything from cosmetics to medications to treat conditions like diabetes and multiple sclerosis. Unlike proteins that are long chains of amino acids, peptides have smaller structures and are able to penetrate the intestines, skin and bloodstream more easily. They are also able to reach the target cells in more precise ways than larger proteins.
Antimicrobial peptides (AMPs) have garnered increasing attention as a potential alternative to antibiotics due to their broad spectrum of activities against various microorganisms and low side effects. A key factor in the success of these drugs is their ability to target and disrupt bacterial cell membranes without disrupting cellular function.
Surface proteins of Staphylococcus aureus bind to peptidoglycan in the bacterial envelope either as a ring-like distribution (clumping factor A, Spa and fibronectin-binding protein B) or at discrete assembly sites within the cell wall (SasA, SasD and SasF). These proteins are directed to their respective destinations by signal peptides with or without the YSIRK/GS motif. Mutations that alter the YSIRK/GS motif do not affect the ring-like distribution of the protein, but do prevent it from binding to the cell wall envelope.
The physicochemical strategy behind cargo recruitment and subsequent intracellular release combines LLPS of a pH-responsive peptide with self-immolative disulfide chemistry. The insertion of a single Lys residue shifts the pH at which HBpep phase-separates by