Structure and function of the bacillithiol‐S‐transferase BstA from Staphylococcus aureus

Abstract

Bacillithiol is a low-molecular weight thiol produced by many gram-positive organisms, including Staphylococcus aureus and Bacillus anthracis. It is the major thiol responsible for maintaining redox homeostasis and cellular detoxification, including inactivation of the antibiotic fosfomycin. The metal-dependent bacillithiol transferase BstA is likely involved in these sorts of detoxification processes, but the exact substrates and enzyme mechanism have not been identified. Here we report the 1.34 Å resolution X-ray crystallographic structure of BstA from S. aureus. Our structure confirms that BstA belongs to the YfiT-like metal-dependent hydrolase superfamily. Like YfiT, our structure contains nickel within its active site, but our functional data suggest that BstA utilizes zinc for activity. Although BstA and YfiT both contain a core four helix bundle and coordinate their metal ions in the same fashion, significant differences between the protein structures are described here.

Low-molecular-weight thiol transferases in redox regulation and antioxidant defence

“…As a member of the STL superfamily, the homodimeric S. aureus BstA has a typical DinB domain comprised of a four-helix bundle (PDB: 5KW0 ) [ 11 , 136 ]. It is a metalloenzyme with a metal ion stabilized by conserved His residues ( Fig.…”

“…It is a metalloenzyme with a metal ion stabilized by conserved His residues ( Fig. 3 C – black circle) [ 136 , 137 ]. A possible dimeric interface involves residues of helices 1 and 4 of each monomer.…”

“…3 C). Although a nickel ion was observed within the structure (due to purification conditions), further studies demonstrated that in the presence of zinc ion, BstA has a higher BSH transferase activity [ 136 ]. Within the putative active site pocket, polar and positively charged residues are present, which may stabilize the negatively charged malate moiety of bacillithiol.…”

“…Within the putative active site pocket, polar and positively charged residues are present, which may stabilize the negatively charged malate moiety of bacillithiol. On the other side of the metal ion, non-polar residues are present, which may participate in the stabilization of electrophilic substrates [ 136 ]. Future studies of BSH-bound and/or electrophilic substrate-bound BstA structure(s) could reveal the detailed BSH and electrophilic substrate binding sites and stabilization interactions.…”

Crystal Structure of the Ergothioneine Sulfoxide Synthase from Candidatus Chloracidobacterium thermophilum and Structure-Guided Engineering To Modulate Its Substrate Selectivity

“…Each monomer is composed of an N-terminal helical domain (residue 17 to 183) and a C-terminal domain that consists of an α–ββ–α fold (residue 194 to 433) (Figure A). A Dali search revealed that the N -terminal domain most closely resembles the damage-inducible protein Din-B (PDB ID: 5WK0 ) and the C -terminal domain is structurally similar to the formylglycine generating enzyme (PDB ID: 5NXL). The C -terminal domain shares a high structural similarity with the catalytic domain of EgtB Mth …”