Biology subjects

Peters, S. C.

Publications and source records attributed to Peters, S. C..

3 recordsLinked to original sources

bioRxiv2025

Copper acquisition in Bacillus subtilis involves Cu(II) exchange between YcnI and YcnJ

The transition metal copper is biologically essential across all three domains of life. Several copper-dependent proteins and enzymes produced by the Gram-positive bacterium Bacillus subtilis have been characterized. However, many questions remain about how copper is recognized and trafficked to metalate cuproproteins. The ycnKJI operon in B. subtilis encodes a suite of proteins implicated in copper uptake and regulation, including the copper-binding protein YcnI and the putative copper importer YcnJ. Here, we demonstrate that one of the extracellular domains within YcnJ (YcnJCopC) binds Cu(II) in 1:1 stoichiometry with high affinity using a histidine brace motif. Biochemical results reveal that YcnJCopC and YcnI can exchange Cu(II). Genetic studies reveal that loss of either YcnI or YcnJ, or mutation of the key residues required for Cu(II)-binding, leads to a growth defect under conditions of copper limitation. Together, these data suggest that the Cu(II)-binding sites in both YcnI and YcnJ contribute to efficient import under Cu limited conditions. Our results support a model in which YcnI may sequester Cu(II) from YcnJ, serving a regulatory role to limit the amount of copper that enters the cytoplasm and allowing Cu(II) to be stored for later import in the outer face of the membrane. This transfer of Cu(II) between extracellular domains of membrane-bound proteins represents a potential new paradigm in bacterial copper usage.

biochemistry↗

bioRxiv2021

SAXS analysis of the intrinsic tenase complex bound to lipid nanodisc highlights intermolecular contacts between factors VIIIa/IXa

The intrinsic tenase (Xase) complex, formed by factors (f)VIIIa and fIXa, forms on activated platelet surfaces and catalyzes the activation of factor X to Xa, stimulating thrombin production in the blood coagulation cascade. The structural organization of the membrane-bound Xase complex remains largely unknown, hindering our understanding of the structural underpinnings that guide Xase complex assembly. Here, we aimed to characterize the Xase complex bound to a lipid nanodisc with biolayer interferometry (BLI) and small angle X-ray scattering (SAXS). Using immobilized lipid nanodiscs, we measured binding rates and nanomolar affinities for fVIIIa, fIXa, and the Xase complex. An ab initio molecular envelope of the nanodisc-bound Xase complex allowed us to computationally model fVIIIa and fIXa docked onto a flexible lipid membrane and identify protein-protein interactions. Our results highlight multiple points of contact between fVIIIa and fIXa, including a novel interaction with fIXa at the fVIIIa A1-A3 domain interface. Lastly, we identified hemophilia A/B-related mutations with varying severities at the fVIIIa/fIXa interface that may regulate Xase complex assembly. Together, our results support the use of SAXS as an emergent tool to investigate the membrane-bound Xase complex and illustrate how mutations at the fVIIIa/fIXa dimer interface may disrupt or stabilize the activated enzyme complex.

biochemistry↗

bioRxiv2021

The YcnI protein from Bacillus subtilis contains a copper-binding domain

Bacteria require a precise balance of copper ions to ensure that essential cuproproteins are fully metalated while also avoiding copper-induced toxicity. The Gram positive bacterium Bacillus subtilis maintains appropriate copper homeostasis in part through its ycn operon. The ycn operon comprises genes encoding three proteins: the putative copper importer YcnJ, the copper-dependent transcriptional repressor YcnK, and the uncharacterized DUF1775 domain-containing YcnI. DUF1775 domains are found across bacterial phylogeny and bioinformatics analyses indicate that they frequently neighbor domains implicated in copper homeostasis and transport. Here, we investigated whether YcnI can interact with copper and, using electron paramagnetic resonance (EPR) and inductively-coupled plasma-mass spectrometry (ICP-MS) find that it can bind a single Cu(II) ion. We determine the structure of both the apo and copper-bound forms of the protein by X-ray crystallography, uncovering a copper binding site featuring a unique mono-histidine brace ligand set that is highly conserved among DUF1775 domains. These data suggest a possible role for YcnI as a copper chaperone and that DUF1775 domains in other bacterial species may also function in copper homeostasis.

biophysics↗