Abstract
Peptidoglycan O‐acetylesterase (Ape1), which is required for host survival in Neisseria sp., belongs to the diverse SGNH hydrolase superfamily, which includes important viral and bacterial virulence factors. Here, multi‐domain crystal structures of Ape1 with an SGNH catalytic domain and a newly identified putative peptidoglycan‐detection module are reported. Enzyme catalysis was performed in Ape1 crystals and key catalytic intermediates along the SGNH esterase hydrolysis reaction pathway were visualized, revealing a substrate‐induced productive conformation of the catalytic triad, a mechanistic detail that has not previously been observed. This substrate‐induced productive conformation of the catalytic triad shifts the established dogma on these enzymes, generating valuable insight into the structure‐based design of drugs targeting the SGNH esterase superfamily.
Highlights
SGNH esterases are ubiquitous enzymes that are involved in a wide range of essential biological processes, for example in viral and bacterial pathogenesis (Lescic Asler et al, 2010)
Their fundamental activity is to catalyze the hydrolysis of an acetyl ester, and they have a broad range of substrate specificities and enzyme–substrate promiscuity (Lescic Asler et al, 2010)
Their active sites all contain four absolutely conserved residues, Ser, Gly, Asn and His, and the catalytic mechanism is predicted to proceed through a nucleophilic Ser which is activated by a catalytic triad that includes the conserved His and an accompanying conserved acidic residue (Lescic Asler et al, 2010; Lo et al, 2003)
Summary
SGNH esterases are ubiquitous enzymes that are involved in a wide range of essential biological processes, for example in viral and bacterial pathogenesis (Lescic Asler et al, 2010). No structural data exist for the Ape family of enzymes or for any enzyme that is involved in PGN acetylation (Weadge et al, 2005), a process that allows pathogenic bacteria to subvert the host innate immune response (Diacovich & Gorvel, 2010; Aubry et al, 2011; Fig. 1a) This modification precludes the normal metabolism and maturation of the peptidoglycan by the endogenous hydrolases of the hexosaminidase superfamily such as lytic transglycosylases (Chan et al, 2012; Bera et al, 2005). Initial phases were found using SHELXC/D/E and the initial model was built using phenix.autobuild with 22 selenium sites and a figure of merit of 0.59 (Adams et al, 2010; Sheldrick, 2008)
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