What is the characteristic feature of cationic peptides like defensins?

Cationic peptides, such as defensins, are characterized primarily by their positive charge. This positive charge arises from the presence of amino acids with basic side chains, such as lysine and arginine. The positive charge plays a critical role in their function, particularly in their ability to interact with negatively charged components of microbial cell membranes, including phospholipids and lipopolysaccharides. This interaction can lead to disruption of the microbial cell membrane, ultimately contributing to the antimicrobial properties of these peptides.

While other options mention features like high affinity for lipids, enzymatic activity, and affinity for DNA, these do not define cationic peptides in the same way the positive charge does. The unique positive charge of defensins and similar peptides is crucial for their protective role in the immune system, enabling them to target and neutralize pathogens effectively.