A considerable proportion of hydrophobic residues at neutral pH. The balance amongst charge distribution and hydrophobicity of AMPs plays an critical role in their function (Melo et al., 2011; Chu et al., 2015; Deslouches and Di, 2017). AMPs could possibly be classified into distinctive categories depending on the different properties which include electrostatic charge, structure, amino acid components, mode of action, and origin (Lei et al., 2019). From the secondary structural point of view, AMPs are classified into 4 categories: -helix, -sheet, extended or random coil, and cyclic or loop peptide (Rajchakit and Sarojini, 2017; Xie et al., 2020). The -helix AMPs would be the most extensively Neurotrophin-3 Proteins Recombinant Proteins studied class with random conformations in aqueous options even though possessing a helical conformation for the duration of interaction with cell membranes (Tornesello et al., 2020). Typical examples ofFrontiers in Cell and Developmental Biology www.frontiersin.orgJuly 2022 FGF-16 Proteins Recombinant Proteins Volume ten ArticleMoeinabadi-Bidgoli et al.Anticancer Effects of MSCs-Derived AMPsthe -helix peptides are human cathelicidin LL-37, histatins, dermcidin, and granulysin (Wang, 2014). The -sheet AMPs are characterized by no less than two -strands containing a single or more disulfide cysteine-cysteine bonds that stabilize the structure and facilitate cell membrane penetration (Wu et al., 2018; Seyfi et al., 2020). Human -defensins and hepcidins are examples of -sheet AMPs (Wang, 2014). Extended AMPs, non- peptides, do not fold into typical secondary structures. They normally comprise a high percentage of specific amino acids, ineffective against cell membranes (Nguyen et al., 2011). The cyclic peptides are the smallest group of AMPs that form closed-loop structures composed of head-to-tail cyclization or disulfide bonds (Xie et al., 2020). AMPs are essential elements in the innate immune response that defend different organisms by inducing a wide range of inhibitory effects for the duration of the initial stages of infection (Ganz, 2003). They show immune responses against numerous microorganisms, like viruses, Gram-positive and Gramnegative bacteria, and fungi. While the molecular mechanisms by which they act aren’t however totally elucidated, their direct effect around the bacterial cell membrane is the most prevalent known activity of AMPs (Huerta-Cantillo and Navarro-Garc , 2016; Lee et al., 2019). In most scenarios, it is notable that the initial interaction with the plasma membrane by means of electrostatic charges is essential (Huerta-Cantillo and Navarro-Garc , 2016). So that you can describe the basis of electrostatic interaction of AMPs using the cell membrane, it has been shown that as opposed to the outer leaflet with the normal eukaryote cell membrane that mainly consists of zero net charged lipids, the outer side of the bacterial membrane includes a greater proportion of lipids using a damaging charge like lipopolysaccharide (LPS) in Gram-negative bacteria and teichoic and teichuronic acids in Gram-positive bacteria. Hence, the cationic surface charges of AMPs are responsible for the electrostatic interactions and binding among AMPs and negatively charged lipids around the target cell membranes (Li et al., 2017). After efficient AMP-membrane interaction, AMPs’ mechanisms of action might be divided into two categories: membrane disruption and non-membrane disruption. Inside the membrane disruption mechanism, AMP-membrane interaction disrupts the bacterial membrane, causing an alteration in membrane permeability, formation of pores, lysis from the mem.