Marlene Mekel

The development of new triazole based inhibitors of tumor necrosis factor-α (TNF-α) production

4-Aryl-3-pyridyl and 4-aryl-3-pyrimidinyl based tumor necrosis factor-alpha (TNF-alpha) inhibitors, which contain a novel isoxazolone five-membered heterocyclic core are described. Many showed sub-micromolar activity against lipopolysaccharide-induced TNF-alpha production.

The Crystal Structures of the Psychrophilic Subtilisin S41 and the Mesophilic Subtilisin Sph Reveal the Same Calcium-Loaded State.

We determine and compare the crystal structure of two proteases belonging to the subtilisin superfamily: S41, a cold‐adapted serine protease produced by Antarctic bacilli, at 1.4 Å resolution and Sph, a mesophilic serine protease produced by Bacillus sphaericus, at 0.8 Å resolution. The purpose of this comparison was to find out whether multiple calcium ion binding is a molecular factor responsible for the adaptation of S41 to extreme low temperatures. We find that these two subtilisins have the same subtilisin fold with a root mean square between the two structures of 0.54 Å. The final models for S41 and Sph include a calcium‐loaded state of five ions bound to each of these two subtilisin molecules. None of these calcium‐binding sites correlate with the high affinity known binding site (site A) found for other subtilisins. Structural analysis of the five calcium‐binding sites found in these two crystal structures indicate that three of the binding sites have two side chains of an acidic residue coordinating the calcium ion, whereas the other two binding sites have either a main‐chain carbonyl, or only one acidic residue side chain coordinating the calcium ion. Thus, we conclude that three of the sites are of high affinity toward calcium ions, whereas the other two are of low affinity. Because Sph is a mesophilic subtilisin and S41 is a psychrophilic subtilisin, but both crystal structures were found to bind five calcium ions, we suggest that multiple calcium ion binding is not responsible for the adaptation of S41 to low temperatures. Proteins 2009.

Engineering the catalytic domain of human protein tyrosine phosphatase beta for structure-based drug discovery.

Protein tyrosine phosphatases (PTPs) play roles in many biological processes and are considered to be important targets for drug discovery. As inhibitor development has proven challenging, crystal structure-based design will be very helpful to advance inhibitor potency and selectivity. Successful application of protein crystallography to drug discovery heavily relies on high-quality crystal structures of the protein of interest complexed with pharmaceutically interesting ligands. It is very important to be able to produce protein-ligand crystals rapidly and reproducibly for as many ligands as necessary. This study details our efforts to engineer the catalytic domain of human protein tyrosine phosphatase beta (HPTPbeta-CD) with properties suitable for rapid-turnaround crystallography. Structures of apo HPTPbeta-CD and its complexes with several novel small-molecule inhibitors are presented here for the first time.

Serendipitous discovery of novel bacterial methionine aminopeptidase inhibitors

In this article we describe the application of structural biology methods to the discovery of novel potent inhibitors of methionine aminopeptidases. These enzymes are employed by the cells to cleave the N‐terminal methionine from nascent peptides and proteins. As this is one of the critical steps in protein maturation, it is very likely that inhibitors of these enzymes may prove useful as novel antibacterial agents. Involvement of crystallography at the very early stages of the inhibitor design process resulted in serendipitous discovery of a new inhibitor class, the pyrazole‐diamines. Atomic‐resolution structures of several inhibitors bound to the enzyme illuminate a new mode of inhibitor binding. Proteins 2007.