Many hospital infections have been difficult to treat due to opportunistic bacterial infections. Many of these bacteria belong to regular microbial flora, making them a real challenge for immune-depressed patients. In general, treatment is expensive and inefficient, encouraging click here several research groups to screen novel antimicrobial compounds [9] and [40]. Among them, antimicrobial peptides (AMPs) have been focused since they are the first natural barrier against microorganisms

from almost all living groups [40]. AMPs are constitutively expressed or induced by endogenous or exogenous elicitors, such as developmental stage or pathogen predation [32]. AMPs are small proteins, 20–50 amino acid residues long, and in some organisms constitute the primary innate host defense line, often have common properties such as the small number of amino acid residues, cationicity and amphipathicity [25]. Although various AMPs have been isolated in different kingdoms, several structural scaffolds

are quite common and may be related to a single promiscuous class of peptides with multiple functions [8]. The mechanism of action include select electrostatic interactions that may induce lipid bilayer depolarization, permeability alterations and ion imbalance [28] that may lead to membrane disruption. Moreover, the presence of AMPs could also lead to alteration of several gene expressions, improving protein synthesis www.selleckchem.com/products/z-vad-fmk.html and modifying enzyme activities [32]. In the last two decades a number of studies have shown that AMPs act synergistically to the immune response [10] and [23], making isolation, identification and characterization of natural AMPs an

important tool for development of a new generation of PLEK2 drugs [11], [23] and [39]. Among the AMPs, the glycine-rich proteins (GRPs) are a group of proteins that occurs in a wide variety of organisms. This group carries glycine-rich repeat domains [2] and [24] and their expressions in plants are normally modulated by abiotic and biotic stresses, showing defensive activity against fungi, bacteria and viruses [2]. Pelegrini et al. [28] demonstrated that a GRP isolated from guava seeds, denominated Pg-AMP1, showed activity against human pathogenic Gram-negative bacteria such as Escherichia coli, Klebsiella sp. and Proteus sp. In spite of the clear bactericidal activity observed, purification and yield of Pg-AMP1 was extremely low, reaching approximately 1 mg of peptide from almost 10 kg of total guava seeds [28]. This protein quantity was insufficient to allow novel experiments or to use these peptides as a biotechnological tool for infectious disease treatment. Furthermore, Pg-AMP1chemical synthesis, a peptide 55 amino acid residues long, is extremely expensive, therefore for Pg-AMP1 the strategy of recombinant protein production in a heterologous system is essential.