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Instruments / Technical Area	Publication Details	Published
I03-Macromolecular Crystallography I04-Macromolecular Crystallography I24-Microfocus Macromolecular Crystallography	Deciphering the molecular mechanism underpinning phage arbitrium communication systems Francisca Gallego Del Sol , José R. Penadés , Alberto Marina Molecular Cell DOI: 10.1016/j.molcel.2019.01.025 Diamond Proposal Number(s): [14739, 20229] Open Access Show Abstract ▼ Abstract: Bacillus phages use a communication system, termed “arbitrium,” to coordinate lysis-lysogeny decisions. Arbitrium communication is mediated by the production and secretion of a hexapeptide (AimP) during lytic cycle. Once internalized, AimP reduces the expression of the negative regulator of lysogeny, AimX, by binding to the transcription factor, AimR, promoting lysogeny. We have elucidated the crystal structures of AimR from the Bacillus subtilis SPbeta phage in its apo form, bound to its DNA operator and in complex with AimP. AimR presents intrinsic plasticity, sharing structural features with the RRNPP quorum-sensing family. Remarkably, AimR binds to an unusual operator with a long spacer that interacts nonspecifically with the receptor TPR domain, while the HTH domain canonically recognizes two inverted repeats. AimP stabilizes a compact conformation of AimR that approximates the DNA-recognition helices, preventing AimR binding to the aimX promoter region. Our results establish the molecular basis of the arbitrium communication system.	Feb 2019
I20-Scanning-X-ray spectroscopy (XAS/XES)	Dimensionality-driven metal–insulator transition in spin–orbit-coupled IrO2 E. Arias-Egido , M. A. Laguna-Marco , C. Piquer , P. Jimenez-Cavero , I. Lucas , L. Morellon , F. Gallego , A. Rivera-Calzada , M. Cabero , J. Santamaría , G. Fabbris , D. Haskel , R. Boada , S. Diaz-Moreno Nanoscale DOI: 10.1039/D1NR04207F Diamond Proposal Number(s): [17266] Open Access Show Abstract ▼ Abstract: A metal–insulator transition is observed in spin–orbit-coupled IrO2 thin films upon reduction of the film thickness. In the epitaxially grown samples, the critical thickness (t ∼ 1.5–2.2 nm) is found to depend on growth orientation (001), (100) or (110). Interestingly from the applied point of view, the insulating behavior is found even in polycrystalline ultrathin films. By analyzing the experimental electrical response with various theoretical models, we find good fits to the Efros–Shklovskii-VRH and the Arrhenius-type behaviors, which suggests an important role of electron correlations in determining the electrical properties of IrO2. Our magnetic measurements also point to a significant role of magnetic order. Altogether, our results would point to a mixed Slater- and Mott-type of insulator.	Oct 2021
I24-Microfocus Macromolecular Crystallography	Insights into the mechanism of action of the arbitrium communication system in SPbeta phages Francisca Gallego Del Sol , Nuria Quiles-Puchalt , Aisling Brady , José R. Penadés , Alberto Marina Nature Communications 13 DOI: 10.1038/s41467-022-31144-3 Diamond Proposal Number(s): [28394] Open Access Show Abstract ▼ Abstract: The arbitrium system is employed by phages of the SPbeta family to communicate with their progeny during infection to decide either to follow the lytic or the lysogenic cycle. The system is controlled by a peptide, AimP, that binds to the regulator AimR, inhibiting its DNA-binding activity and expression of aimX. Although the structure of AimR has been elucidated for phages SPβ and phi3T, there is still controversy regarding the molecular mechanism of AimR function, with two different proposed models for SPβ. In this study, we deepen our understanding of the system by solving the structure of an additional AimR that shows chimerical characteristics with the SPβ receptor. The crystal structures of this AimR (apo, AimP-bound and DNA-bound) together with in vitro and in vivo analyses confirm a mechanism of action by AimP-induced conformational restriction, shedding light on peptide specificity and cross regulation with relevant biological implications.	Jun 2022
I24-Microfocus Macromolecular Crystallography	Rationally designed antifungal protein chimeras reveal new insights into structure-activity relationship Moisés Giner-Llorca , Francisca Gallego Del Sol , Jose F. Marcos , Alberto Marina , Paloma Manzanares International Journal Of Biological Macromolecules 100 DOI: 10.1016/j.ijbiomac.2022.11.280 Diamond Proposal Number(s): [28394] Open Access Show Abstract ▼ Abstract: Antifungal proteins (AFPs) are promising antimicrobial compounds that represent a feasible alternative to fungicides. Penicillium expansum encodes three phylogenetically distinct AFPs (PeAfpA, PeAfpB and PeAfpC) which show different antifungal profiles and fruit protection effects. To gain knowledge about the structural determinants governing their activity, we solved the crystal structure of PeAfpB and rationally designed five PeAfpA::PeAfpB chimeras (chPeAFPV1-V5). Chimeras showed significant differences in their antifungal activity. chPeAFPV1 and chPeAFPV2 improved the parental PeAfpB potency, and it was very similar to that of PeAfpA. chPeAFPV4 and chPeAFPV5 showed an intermediate profile of activity compared to the parental proteins while chPeAFPV3 was inactive towards most of the fungi tested. Structural analysis of the chimeras evidenced an identical scaffold to PeAfpB, suggesting that the differences in activity are due to the contributions of specific residues and not to induced conformational changes or structural rearrangements. Results suggest that mannoproteins determine protein interaction with the cell wall and its antifungal activity while there is not a direct correlation between binding to membrane phospholipids and activity. This work provides new insights about the relevance of sequence motifs and the feasibility of modifying protein specificity, opening the door to the rational design of chimeras with biotechnological applicability.	Nov 2022

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