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Publication Abstract from PubMed

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 A 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. Most organisms employ low-molecular weight thiols (LMWTs) to serve as redox buffers and deactivate toxic compounds. Bacillithiol (Scheme S1) is the predominant LMWT in many gram-positive bacteria such as Staphylococcus aureus and Bacillus anthracis.(1-3) It is the preferred thiol cosubstrate for FosB, a bacillithiol-S-transferase responsible for resistance to the antibiotic fosfomycin.(4,5) BstA is another bacillithiol-S-transferase from S. aureus that plays a role in detoxifying electrophilic xenobiotic compounds within the cell by producing bacillithiol-S-conjugated products, which are further processed and removed from the cell.(6) BstA is active against the model electrophilic compound chloro-2,4-dinitrobenzene (CDNB), but the exact electrophilic substrate, or group of substrates, upon which BstA acts has not been identified. BstA belongs to the DinB/YfiT-like superfamily of metal-dependent enzymes.(6,7) Although the structure of the namesake bacillithiol transferase YfiT from B. subtilis has been determined,(8) the study of bacillithiol transferases is still in its infancy, and additional structures are needed to characterize this group of enzymes. Here we present the 1.34 A resolution crystal structure of BstA from S. aureus. The structure clearly demonstrates how the enzyme binds its metal cofactor and gives insight into the types of substrates BstA might bind. Furthermore, we demonstrate that BstA is likely zinc-dependent. This article is protected by copyright. All rights reserved.

Structure and Function of the Bacillithiol-S-Transferase BstA from Staphylococcus aureus.,Francis JW, Royer CJ, Cook PD Protein Sci. 2018 Feb 8. doi: 10.1002/pro.3384. PMID:29417696^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.