title: Protein surface charge of trypsinogen changes its activation pattern.
abstract: BACKGROUND
  Trypsinogen is the inactive precursor of trypsin, a serine protease that cleaves proteins and peptides after arginine and lysine residues. In this study, human trypsinogen was used as a model protein to study the influence of electrostatic forces on protein-protein interactions. Trypsinogen is active only after its eight-amino-acid-long activation peptide has been cleaved off by another protease, enteropeptidase. Trypsinogen can also be autoactivated without the involvement of enteropeptidase. This autoactivation process can occur if a trypsinogen molecule is activated by another trypsin molecule and therefore is based on a protein-protein interaction.
  
  
  RESULTS
  Based on a rational protein design based on autoactivation-defective guinea pig trypsinogen, several amino acid residues, all located far away from the active site, were changed to modify the surface charge of human trypsinogen. The influence of the surface charge on the activation pattern of trypsinogen was investigated. The autoactivation properties of mutant trypsinogen were characterized in comparison to the recombinant wild-type enzyme. Surface-charged trypsinogen showed practically no autoactivation compared to the wild-type but could still be activated by enteropeptidase to the fully active trypsin. The kinetic parameters of surface-charged trypsinogen were comparable to the recombinant wild-type enzyme.
  
  
  CONCLUSIONS
  The variant with a modified surface charge compared to the wild-type enzyme showed a complete different activation pattern. Our study provides an example how directed modification of the protein surface charge can be utilized for the regulation of functional protein-protein interactions, as shown here for human trypsinogen.
authors.affiliation: Institute of Bioanalytical Chemistry, Center for Biotechnology and Biomedicine, Universität Leipzig, 04103, Leipzig, Germany. karin.buettner@uni-leipzig.de.
authors.forename: Karin
authors.initials: K
authors.lastname: Buettner
authors.affiliation: Institute of Bioanalytical Chemistry, Center for Biotechnology and Biomedicine, Universität Leipzig, 04103, Leipzig, Germany. thomas.kreisig@bbz.uni-leipzig.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kreisig
authors.affiliation: Institute of Bioanalytical Chemistry, Center for Biotechnology and Biomedicine, Universität Leipzig, 04103, Leipzig, Germany. strater@bbz.uni-leipzig.de.
authors.forename: Norbert
authors.initials: N
authors.lastname: Sträter
authors.affiliation: Institute of Bioanalytical Chemistry, Center for Biotechnology and Biomedicine, Universität Leipzig, 04103, Leipzig, Germany. Thole.Zuechner@octapharma.com.|Current address: Octapharma Biopharmaceuticals GmbH, Im Neuenheimer Feld 590, Heidelberg, 69120, Germany. Thole.Zuechner@octapharma.com.
authors.forename: Thole
authors.initials: T
authors.lastname: Zuchner
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D004789:Enzyme Activation; D006168:Guinea Pigs; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D014357:Trypsin / Q000378:metabolism; D014362:Trypsinogen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D014362:Trypsinogen; D014357:Trypsin