Serine bacteriolytic protease L1 of Lysobacter sp. XL1 complexed with protease inhibitor AEBSF: features of interaction

Abstract Extracellular bacteriolytic enzymes of bacteria break down peptidoglycan of competitive microorganisms. This group of enzymes has been investigated rather poorly. To understand how the active site of the bacteriolytic protease L1 of Lysobacter sp. XL1 operates, we determined the structure of this enzyme in complex with serine protease inhibitor 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF). Proceeding from the structural data, part of L1 molecules was shown to interact with the inhibitor to form a covalent bond with the serine residue of the (Ser144)O–S(AEBSF) catalytic centre, and the other part formed a hydrogen bond (Ser144)–(AEBSF). Inhibitor analysis revealed enzyme L1 to be capable of partially restoring its activity, which confirms the X-ray diffraction data on the formation of a less strong bond to the inhibitor in part of the molecules of L1.