| 1. |
- Bozzola, Tiago, et al.
(författare)
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Sialic Acid Derivatives Inhibit SiaT Transporters and Delay Bacterial Growth
- 2022
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Ingår i: Acs Chemical Biology. - : American Chemical Society (ACS). - 1554-8929 .- 1554-8937. ; 17:7, s. 1890-1900
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Tidskriftsartikel (refereegranskat)abstract
- Antibiotic resistance is a major worldwide concern, and new drugs with mechanistically novel modes of action are urgently needed. Here, we report the structure-based drug design, synthesis, and evaluation in vitro and in cellular systems of sialic acid derivatives able to inhibit the bacterial sialic acid symporter SiaT. We designed and synthesized 21 sialic acid derivatives and screened their affinity for SiaT by a thermal shift assay and elucidated the inhibitory mechanism through binding thermodynamics, computational methods, and inhibitory kinetic studies. The most potent compounds, which have a 180-fold higher affinity compared to the natural substrate, were tested in bacterial growth assays and indicate bacterial growth delay in methicillin-resistant Staphylococcus aureus. This study represents the first example and a promising lead in developing sialic acid uptake inhibitors as novel antibacterial agents.
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| 2. |
- Coombes, D., et al.
(författare)
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The basis for non-canonical ROK family function in the N-acetylmannosamine kinase from the pathogen Staphylococcus aureus
- 2020
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 295:10, s. 3301-3315
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Tidskriftsartikel (refereegranskat)abstract
- In environments where glucose is limited, some pathogenic bacteria metabolize host-derived sialic acid as a nutrient source. N-Acetylmannosamine kinase (NanK) is the second enzyme of the bacterial sialic acid import and degradation pathway and adds phosphate to N-acetylmannosamine using ATP to prime the molecule for future pathway reactions. Sequence alignments reveal that Gram-positive NanK enzymes belong to the Repressor, ORF, Kinase (ROK) family, but many lack the canonical Zn-binding motif expected for this function, and the sugar-binding EXGH motif is altered to EXGY. As a result, it is unclear how they perform this important reaction. Here, we study the Staphylococcus aureus NanK (SaNanK), which is the first characterization of a Gram-positive NanK. We report the kinetic activity of SaNanK along with the ligand?free, N-acetylmannosamine?bound and substrate analog GlcNAc?bound crystal structures (2.33, 2.20, and 2.20 ? resolution, respectively). These demonstrate, in combination with small-angle X-ray scattering, that SaNanK is a dimer that adopts a closed conformation upon substrate binding. Analysis of the EXGY motif reveals that the tyrosine binds to the N-acetyl group to select for the ?boat? conformation of N-acetylmannosamine. Moreover, SaNanK has a stacked arginine pair coordinated by negative residues critical for thermal stability and catalysis. These combined elements serve to constrain the active site and orient the substrate in lieu of Zn binding, representing a significant departure from canonical NanK binding. This characterization provides insight into differences in the ROK family and highlights a novel area for antimicrobial discovery to fight Gram-positive and S. aureus infections.
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| 3. |
- Davies, James S., et al.
(författare)
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Structure and mechanism of a tripartite ATP-independent periplasmic TRAP transporter
- 2023
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- In bacteria and archaea, tripartite ATP-independent periplasmic (TRAP) transporters uptake essential nutrients. TRAP transporters receive their substrates via a secreted soluble substrate-binding protein. How a sodium ion-driven secondary active transporter is strictly coupled to a substrate-binding protein is poorly understood. Here we report the cryo-EM structure of the sialic acid TRAP transporter SiaQM from Photobacterium profundum at 2.97 Å resolution. SiaM comprises a “transport” domain and a “scaffold” domain, with the transport domain consisting of helical hairpins as seen in the sodium ion-coupled elevator transporter VcINDY. The SiaQ protein forms intimate contacts with SiaM to extend the size of the scaffold domain, suggesting that TRAP transporters may operate as monomers, rather than the typically observed oligomers for elevator-type transporters. We identify the Na+ and sialic acid binding sites in SiaM and demonstrate a strict dependence on the substrate-binding protein SiaP for uptake. We report the SiaP crystal structure that, together with docking studies, suggest the molecular basis for how sialic acid is delivered to the SiaQM transporter complex. We thus propose a model for substrate transport by TRAP proteins, which we describe herein as an ‘elevator-with-an-operator’ mechanism.
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