Systematic Design of Histone-Derived Antimicrobial Peptides

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Project Summary Bacteria that have developed resistance to conventional antibiotics are an increasing public health concern, and antimicrobial peptides (AMPs) represent a potential alternative to combat these bacteria. One intriguing family of AMPs is the histone-derived antimicrobial peptides (HDAPs). HDAPs have been isolated from natural sources, and the mechanisms for many of these peptides have been determined experimentally. However, relatively little focus has been given to the rational optimization and design of HDAPs to engineer more active peptides. This proposal aims to address this gap through purposeful and design-motivated investigations of three additional factors that we hypothesize will impact HDAP activity: peptide truncations, the formation of hybrid peptides, and combination therapy with antibiotic+AMP cocktails. We are employing a carefully selected set of four representative HDAPs, BF2 and three designed peptides DesHDAP1, DesHDAP2 and DesHDAP3A. These peptides were chosen to span the two broad categories for AMP interaction with cell membranes—peptides that translocate across plasma membranes (BF2 and DesHDAP1) and those that induce significant membrane permeabilization (DesHDAP2 and DesHDAP3A). These peptides also reflect a range of initial antibacterial activities. Thus, we feel that they provide a tractable sample size that nonetheless provide sufficient molecular diversity to identify trends. Our methods include a combination of bacterial and eukaryotic assays, confocal microscopy, spectroscopic measurements, and molecular dynamics simulations. After elucidating trends for our three proposed factors that affect HDAP activity with our representative set of four peptides, we will combine this information to create a novel series of peptides identified from histone sequences through a library-based approach that optimizes the individual factors for peptide activity. We can thus assess the generalizability of our trends to validate whether this is a useful approach for peptide design in HDAPs. These studies will promote the development of HDAPs as potential therapeutic agents and provide insights into HDAP structure-function relationships that potentially can be expanded to other AMP families. In addition to these scientific goals, this research also has a strong emphasis on training as the work will be carried out by several undergraduate researchers and a few recent graduates at Wellesley College, an undergraduate-only women’s college.