It has been demonstrated that in the LPS-neutralizing peptide, the lipid A binding motif includes a cluster of hydrophobic residues encompassed by basic 17-AAG mw aminoacids [14]. More recently, other authors underlined the pivotal role of a group of positively charged central residues with hydrophobic aminoacids distributed in the periphery [15]. The whole PCT used in our study, exhibited a plausible lipid A binding sequence between Pro82 and Pro91[14]. Also a putative lipid A binding sequence can be found between Leu101 and Val109[15] as illustrated in Figure 5. Figure 5 Putative LPS binding sites on PCT molecule. Proposed LPS binding sites include: i) 2–3

cationic aminoacids within a cluster of four (aminoacids 58–59 and aminoacids 93–95), ii) a cluster of hydrophobic residues encompassed by basic aminoacids (82–92), iii) a group of positively Selleckchem ACP-196 charged central residues with hydrophobic aminoacids in the periphery (101–109). Hydrophobic aminoacids in blue, cationic aminoacids in red and other aminoacids in orange. The LPS binding sites suggested by Japelj [14] and Bhattacharjya [15] are indicated. Close to the proposed LPS binding sites, a deep rough LPS chemical structure is showed. Flat dashed lines indicate the limits of the three post-translational processing products (N-ProCT, calcitonin and katacalcin)

of procalcitonin, while dashed forks encompass SB203580 cost the peptides cleaved during post-translational processing [1, 3]. It has also been reported that the need for structural amphipathicity is probably not as an essential feature for LPS binding/neutralization as is the proximity of certain aminoacids (cationic and hydrophobic residues) within a given sequence [16]. The effects of PCT on LPS reactivity in the LAL test model suggest that PCT is equally active against both rough and smooth chemotypes.

The S. typhimurium strain SL1102 exhibits a Re chemotype LPS (deep rough) that has been previously reported as very toxic in an in vivo experimental model [17]. The E. coli 0111:B4 has a smooth chemotype endotoxin often used in studies regarding LPS binding/neutralization [18]. Therefore about PCT targets the lipid A portion which is a common structural feature of these LPSs. Since the molecular weight of PCT is approximately 13,000 daltons and the molecular weight of deep rough LPS is 3,000 daltons, the optimal ratio 5:1 (w/w) associated with LPS neutralization and cytokine inhibition would suggest a 1mole:1mole interaction between PCT and LPS, which could use any of the above mentioned interaction sites available on the PCT molecule. Moreover, our results provide the first evidence of the capability of PCT to significantly decrease the LPS-stimulated release of the Treg cytokine IL-10 and chemokine MCP-1 from human PBMC.