Description:
<jats:p>The Gram‐negative bacterium <jats:italic>Aeromonas salmonicida</jats:italic> is a fish pathogen for various fish species worldwide. <jats:italic>Aeromonas salmonicida</jats:italic> subsp. <jats:italic>achromogenes</jats:italic> produces the extracellular, toxic zinc endopeptidase AsaP1. Crystal structure analyses at 2.0 Å resolution of two proteolytically inactive AsaP1 variants show the polypeptide folding of the protease domain and the propeptide domain. These first crystal structure analyses of a precursor of a deuterolysin‐like aspzincin protease provide insights into propeptide function, and specific substrate binding. A lysine side chain of the propeptide binds in the hydrophobic S1’‐pocket interacting with three carboxylate side chains. An AsaP1 variant with a lysine to alanine exchange identifies the chaperone function of the propeptide.</jats:p>