In vitro and have evolved NET evasion mechanisms which may overcome this potential clearance mechanism [83, 84]. autoantigen, but PR3 is involved in triggering inflammatory pathways, disrupting cellular signalling, degrading key structural proteins, and pathogen response. This TC-E 5006 review summarises what is presently known about PR3, explores its involvement particularly in the development of COPD, and indicates areas requiring further investigation. which TC-E 5006 is located at human chromosome 19p13.3 and spans 6.57?kb pairs including 5 exons and 4 introns. The gene consists of 222 amino acids that fold to form the 29?kDa glycoprotein PR3 [4]. PR3 is classified within the family of chymotrypsin-like neutrophil serine proteinase (NSP) which are identified by their highly conserved catalytic triads (His57, Asp102 and Ser195; using chymotrypsinogen numbering) for proteolytic activity and defined by their active site serine residue [4, 12]. PR3 possesses an enlarged binding site with high specificity and differs from NE by 4 main subsites, S2, S1, S2 and S3 (Fig.?1). which is common to other NSPs, including NE [12]. However, PR3, specificity is further defined by difference in residues which alter subsite specificities (subsites shown in Fig. ?Fig.11). Open in a separate window Fig. 1 Diagrammatically demonstrates the substrate binding pockets S4-S3 of PR3 with substrate cleavage positions P4-P3, according to the Schechter and Berger enzyme-ligand binding site numbering convention [19]. The arrows indicate the sites for Val/Ala-containing peptide cleavage and hydrophobic residue binding sites, whilst + indicates positive and C indicates negative residue binding site. Adapted from [13] These specificities are determined by: Amide hydrogens on Gly193 and Ser195 which stabilise TC-E 5006 charge during catalysis [14]. 3 charged residues: Lys99, Asp61, Arg143 within the active site region. Positioning of the solvent accessible Lys99 (compared to Leu99 in NE), which borders the S2 and S4 sites and makes the S2 subsite deeper and more polar, in addition to reducing its hydrophobicity, which determines preferential binding of negative and polar residues, such as Asp [12, 16, 17]. Asp61 brings the proteins negatively charged side chain closer to the S1 and S3 subsites, making the subsites smaller and more polar, which encourages binding of basic residues at P1 and P3 [12, 16]. Arg143 (and Pro151) increase the polarity of the S2 subsite which creates a basic S2 subsite that binds acidic residues [12, 16]. Asp213 (compared to Ala213 in NE) restricts the S1 binding site causing it to preferably bind small TC-E 5006 hydrophobic residues at P1, which includes alanine, serine, valine, norvaline, and methionine [12, 14, 16C18]. Ile217 allows small hydrophobic residues at P4 to bind whilst with Trp218 creating a more hydrophobic S5 subsite [12, 14, 16]. PR3 is initially transcribed as an inactive precursor referred to as a zymogen and then undergoes a two-stage posttranslational modification to become active. Firstly (via signal peptidase), Pten there is N-terminal signal peptide cleavage, followed by cleavage of the N-terminal pro-di-peptide by the cysteine proteinase, cathepsin C which is essential for enzymatic activity. Secondly it undergoes pro-peptide cleavage at the C terminal, which is crucial for granule packaging. This forms the catalytic triad of residues and the final conformation of mature PR3, as shown in Fig.?2, which is stabilised by disulphide bonds and appropriate asparagine-linked glycosylation [4, 12, 20]. PR3 then remains TC-E 5006 stored within the neutrophil azurophil granules until release. Open in a separate window Fig. 2 Three-dimensional visualisation of Proteinase 3 by ribbon plot, with the catalytic triad and PR3-specific residues stylised in a stick representation and annotated. Image developed from.

In vitro and have evolved NET evasion mechanisms which may overcome this potential clearance mechanism [83, 84]