A common feature ascribed to AMP is their ability to interact with the negatively charged bacterial membranes and polyanionic cell surface (lipopolysaccharide (LPS) of Gram-negative and lipoteichoic acid of Gram-positive bacteria). At their lethal concentrations in vitro, they generally disrupt membrane integrity and cause bacterial lysis. Some

AMP, however, do not cause membrane disruption, but act on intracellular https://www.selleckchem.com/products/gdc-0068.html targets such as nucleic acids [19]. We are studying the human multifunctional innate defense molecule known as pre-elafin/trappin-2. This protein is composed of two domains, an N-terminal AG-881 order moiety of 38 aa known as cementoin based on its ability to be cross-linked to extracellular matrix proteins through the Selleck AZD5363 action of a transglutaminase and a C-terminal part of 57 aa, or elafin domain, that displays sequence similarity with whey acidic protein (WAP) [20]. This latter domain is a potent and specific inhibitor of neutrophil elastase (NE) and myeloblastin, as well as pancreatic elastase [21, 22]. Its structure was determined both by X-ray crystallography in complex with pancreatic elastase and free in solution by nuclear magnetic resonance

(NMR) spectroscopy [23, 24]. The salient structural feature of elafin is a β-sheet stabilized by three disulfide bridges along with an inhibitory loop connected to the central β-sheet by a fourth disulfide bridge. There is no structural information regarding the cementoin domain or the full-length pre-elafin molecule. Apart from the well-known inhibitory

and anti-inflammatory properties of pre-elafin/trappin-2, previous studies also established that the full-length molecule and each of its domains possess broad antimicrobial RG7420 mouse activity, namely against the bacteria P. aeruginosa and S. aureus, and the yeast C. albicans [25–28]. Furthermore, adenoviral overexpression of pre-elafin/trappin-2 in a mouse model of acute P.aeruginosa infection was shown to reduce the bacterial load and to facilitate clearance of the microorganism [29]. Although it has been documented that the full-length molecule is more active than its constituent domains in vitro [25, 27, 28], the exact mechanism of action of each of these peptides against microbial infections is largely unknown. We recently reported that the variable sensitivity of P. aeruginosa strains to pre-elafin/trappin-2 could be partly explained by the specific inhibition of a peptidase secreted by some, but not all, strains by the elafin domain [27]. However, both domains also display antimicrobial activity independent from the peptidase inhibitory function of elafin suggesting that the antimicrobial properties of these peptides are the sum of several unique attributes [27, 28]. In the present study we have determined the secondary structures of the cementoin peptide in the presence or absence of membrane mimetics.