Crystallization and preliminary analysis of neurolysin

Neuropeptidases inactivate or modify the activity of peptide neurotransmitt ers and neurohormones. The neuropeptidase neurolysin acts only on short pep tides and accepts a variety of cleavage-site sequences. Structures of the e nzyme and enzyme-substrate complexes will help to determine the mechanisms of substrate selectivity used by this enzyme. Crystals of recombinant neuro lysin have been grown in the orthorhombic space group P2(1)2(1)2, with unit -cell parameters a = 157.8, b = 88.0, c = 58.4 Angstrom. Data have been col lected to 2.3 Angstrom at 110 K with observed diffraction to 1.8 Angstrom. Circular dichroism measurements suggest that the enzyme is primarily alpha -helical, with little beta -strand secondary structure. Sequence-based seco ndary-structure prediction supports this conclusion.