Structural evidence of intramolecular propeptide inhibition of the aspzincin metalloendopeptidase AsaP1

The Gram-negative bacterium Aeromonas salmonicida is a fish pathogen for various fish species worldwide. Aeromonas salmonicida subsp. Achromogenes produces the extracellular, toxic zinc endopeptidase AsaP1. Crystal structure analyses at 2.0 A 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.