Antimicrobial peptides and proteins (AMPs) are a class of naturally occurring biomolecules found in all multicellular organisms, and are used as a first line of defense for these organisms. A broad collection of AMPs have been discovered that can selectively kill bacteria, yeasts, fungi, viruses, and even cancer cells. Insects and plants utilize AMPs to protect themselves against certain pathogenic microbes, and some microbes will also produce AMPs as a defense mechanism. Typically, AMPs are 10 to 50 amino acids residues in length, and have an overall positive charge. These cationic biomolecules are composed of different distributions of basic and hydrophobic amino acid residues, and typically form α-helical structures that are water soluble, positively charged, and hydrophobic. Because of these properties, AMPs are able to selectively bind to the negatively charged membranes of bacteria, and the selectivity comes from difference in membrane composition of different microbes and cell types. This binding, caused by electrostatic interactions, can result in the direct killing of a microbe, either by rupturing the membrane or inhibiting intracellular function, both paths resulting in bacterial lysis. LL-37 belongs to a peptide subgroup called cathelicidins, which are small, cationic, amphiphilic AMPs found in many species of vertebrates. They are part of the organism’s innate immunity, and have a broad range of antimicrobial activity against fungi, bacteria, and enveloped viruses. Cathelicidin LL-37 is an effector molecule that allows for innate immunity in the skin. If the expression of cathelicidin LL-37 is defective, the result may be atopic dermatitis, psoriasis, or rosacea. Cathelicidin LL-37 treatment may become a novel strategy to combat the previously mentioned illnesses. The primary goal of our work is to optimize the expression and purification of AMP LL-37, utilizing the small ubiquitin-related modifier (SUMO) tag to enhance the expression and stability of the LL-37. Cloning was achieved using the ThermoFisher Champion pET SUMO Protein Expression System, and the LL-37-SUMO peptide was expressed in E. coli.

Optimization of expression and purification of cathelicidin LL37 with the SUMO tag

ACS Spring Meeting 2021

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