Cationic Peptide Interactions with Biological Macromolecules

Cationic amphiphilic peptides (CAPs) are widely studied as effectors that are activated by microbial pathogens in immune signaling pathways of invertebrates and vertebrates. These peptides are non-specific effectors that can kill bacteria, fungi, viruses and protozoan parasites [1, 2]. They are a universal feature in all forms of life and are often found in all the major barriers such as the skin and epithelia that are naturally designed for protection against invading microorganisms. In the case of invertebrates, they play a pivotal role in innate immunity upon which these animals depend for defense against infection. The two immunes response strategies are interdependent and innate immunity has significant impact on the development of adaptive immunity [3-6]. In addition to innate immunity, vertebrates also rely on acquired immunity which is mediated by antibodies and cytotoxic T lymphocytes [7]. Identification of these antimicrobial peptides and the study of their structural features have led to the development of peptide drugs, sometimes through the design of synthetic peptides based on the known structures of the natural ones. A subset of cationic peptides has been found to have anti-tumour as well as wound-healing properties extending the prospects of these peptides as templates for drug design strategies against cancer and wound treatment [8]. The mechanisms by which these latter properties are manifested are not fully understood. Indeed, the mechanisms by which cationic peptides exert their wide biological activities are still under investigation and many theories have been proposed.