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International audience; The interaction between the Shiga toxin B-subunit (STxB) and its globotriaosylceramide receptor (Gb3) has a high potential for being exploited for targeted cancer therapy. The primary goal of this study was to evaluate the capacity of STxB to carry small molecules and proteins as cargo into cells. For this purpose, an assay was designed to provide real-time information about the StxB-Gb3 interaction as well as the dynamics and mechanism of the internalization process. The assay revealed the ability to distinguish the process of binding to the cell surface from internalization and presented the importance of receptor and STxB clustering for internalization. The overall setup demonstrated that the binding mechanism is complex, and the concept of affinity is difficult to apply. Hence, time-resolved methods, providing detailed information about the interaction of STxB with cells, are critical for the optimization of intracellular delivery.

Lipases show high stability in lipophilic solvents and catalyze reactions at the water-oil interfaces, which are of great industrial interest. One promising application of lipases is the production of epoxides from alkenes and hydrogen peroxide. So far, little attention has been given to uncover the reaction mechanism for this in detail at the molecular level. Here, we present structural and mutational analysis of a lipase from Penicillium camembertii that indicates a two-stage synergistic mechanism for this reaction. Surprisingly, a mutant devoid of the catalytic serine retains a fraction of activity while histidine from the catalytic triad is absolutely critical to maintain the enzyme activity. Histidine appears to perform a dual-activation role acting both towards hydrogen peroxide and the catalytic serine. These results thus allow a better understanding of enzymatic epoxidation and engineering of more potent, stable and selective enzymes.

Staphylococcus aureus is responsible for a variety of human infections, including life-threatening, systemic conditions. Secreted proteome, including a range of proteases, constitutes the major virulence factor of the bacterium. However, the functions of individual enzymes, in particular SplA protease, remain poorly characterized. Here, we report development of specific inhibitors of SplA protease. The design, synthesis, and activity of a series of α-aminoalkylphosphonate diaryl esters and their peptidyl derivatives are described. Potent inhibitors of SplA are reported, which may facilitate future investigation of physiological function of the protease. The binding modes of the high-affinity compounds Cbz-PheP-(OC6H4−4-SO2CH3)2 and Suc-Val-Pro-PheP-(OC6H5)2 are revealed by high-resolution crystal structures of complexes with the protease. Surprisingly, the binding mode of both compounds deviates from previously characterized canonical interaction of α-aminoalkylphosphonate peptidyl derivatives and family S1 serine proteases.

The p53 protein is the cell’s principal bastion of defense against tumor-associated DNA damage. Commonly referred as a “guardian of the genome”, p53 is responsible for determining the fate of the cell when the integrity of its genome is damaged. The development of tumors requires breaching this defense line. All known tumor cells either mutate the p53 gene, or in a similar number of cases, use internal cell p53 modulators, Mdm2 and Mdmx proteins, to disable its function. The release of functional p53 from the inhibition by Mdm2 and Mdmx should in principle provide an efficient, nongenotoxic means of cancer therapy. In recent years substantial progress has been made in developing novel p53-activating molecules thanks to several reported crystal structures of Mdm2/x in complex with p53-mimicking peptides and nonpeptidic drug candidates. Understanding the structural attributes of ligand binding holds the key to developing novel, highly effective, and selective drug candidates. Two low-molecular-weight compounds have just recently progressed into early clinical studies.

Das zellulare p53-Protein ist das Bollwerk im Kampf gegen Tumor-assoziierte DNA-Schaden. Allgemein auch als “Beschutzer des Genoms” bekannt, ist p53 fur das Schicksal der Zelle verantwortlich, wenn eine substanzielle DNA-Schadigung vorliegt. Tumoren konnen sich nur entwickeln, wenn diese Verteidigungslinie durchbrochen wird. Alle bekannten Tumorzellen mutieren das p53-Gen oder nutzen interne p53-Modulatoren, wie die beiden Proteine Mdm2 und Mdmx, um p53 zu desaktivieren. Das Freisetzen von p53 aus den Komplexen mit Mdm2 oder Mdmx sollte daher eine effiziente und nicht gentoxische Krebstherapie ermoglichen. Dank mehrerer Kristallstrukturen von Mdm2/x im Komplex mit p53-imitierenden Molekulen, sowohl Peptiden als auch niedermolekularen Verbindungen, gab es in den letzten Jahren fundamentale Fortschritte bei der Entwicklung neuer p53-aktivierender Molekule. Das Verstandnis der Bindungseigenschaften des Liganden ermoglicht die Entwicklung neuer, hoch aktiver und selektiver Wirkstoff-Kandidaten. Zwei niedermolekulare Verbindungen werden seit Kurzem in klinischen Studien untersucht.