title: Structures of neutrophil serine protease 4 reveal an unusual mechanism of substrate recognition by a trypsin-fold protease.
abstract: Trypsin-fold proteases, the largest mammalian protease family, are classified by their primary substrate specificity into one of three categories, trypsin-like, chymotrypsin-like, and elastase-like, based on key structural features of their active site. However, the recently discovered neutrophil serine protease 4 (NSP4, also known as PRSS57) presents a paradox: NSP4 exhibits a trypsin-like specificity for cleaving substrates after arginine residues, but it bears elastase-like specificity determining residues in the active site. Here we show that NSP4 has a fully occluded S1 pocket and that the substrate P1-arginine adopts a noncanonical "up" conformation stabilized by a solvent-exposed H-bond network. This uncommon arrangement, conserved in all NSP4 orthologs, enables NSP4 to process substrates after both arginine as well as post-translationally modified arginine residues, such as methylarginine and citrulline. These findings establish a distinct paradigm for substrate recognition by a trypsin-fold protease and provide insights into the function of NSP4.
authors.affiliation: Department of Early Discovery Biochemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: S Jack
authors.initials: SJ
authors.lastname: Lin
authors.affiliation: Department of Structural Biology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: Ken C
authors.initials: KC
authors.lastname: Dong
authors.affiliation: Department of Structural Biology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Eigenbrot
authors.affiliation: Department of Immunology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
authors.forename: Menno
authors.initials: M
authors.lastname: van Lookeren Campagne
authors.affiliation: Department of Early Discovery Biochemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA. Electronic address: dak@gene.com.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kirchhofer
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D006801:Humans; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D011485:Protein Binding; D012697:Serine Endopeptidases / Q000737:chemistry*; D013379:Substrate Specificity
chemical_list: D012697:Serine Endopeptidases