Martine Stihle

Bio: Martine Stihle is an academic researcher from Hoffmann-La Roche. The author has contributed to research in topics: Carnitine & Ligand (biochemistry). The author has an hindex of 23, co-authored 36 publications receiving 2852 citations.

Unique carbohydrate–carbohydrate interactions are required for high affinity binding between FcγRIII and antibodies lacking core fucose

Abstract: Antibody-mediated cellular cytotoxicity (ADCC), a key immune effector mechanism, relies on the binding of antigen–antibody complexes to Fcγ receptors expressed on immune cells. Antibodies lacking core fucosylation show a large increase in affinity for FcγRIIIa leading to an improved receptor-mediated effector function. Although afucosylated IgGs exist naturally, a next generation of recombinant therapeutic, glycoenginereed antibodies is currently being developed to exploit this finding. In this study, the crystal structures of a glycosylated Fcγ receptor complexed with either afucosylated or fucosylated Fc were determined allowing a detailed, molecular understanding of the regulatory role of Fc-oligosaccharide core fucosylation in improving ADCC. The structures reveal a unique type of interface consisting of carbohydrate–carbohydrate interactions between glycans of the receptor and the afucosylated Fc. In contrast, in the complex structure with fucosylated Fc, these contacts are weakened or nonexistent, explaining the decreased affinity for the receptor. These findings allow us to understand the higher efficacy of therapeutic antibodies lacking the core fucose and also suggest a unique mechanism by which the immune system can regulate antibody-mediated effector functions.

Systematic Investigation of Halogen Bonding in Protein–Ligand Interactions

Abstract: Halogen bonding (XB) refers to the noncovalent interaction of general structure DX···A between halogen-bearing compounds (DX: XB donor, where X=Cl, Br, I) and nucleophiles (A: XB acceptor). Since the first observation in cocrystal structures of 1,4-dioxane and Br2 by Hassel and Hvoslef in 1954, XB has been widely used in crystal engineering and solid-state supramolecular chemistry. The nature of the interaction and the underlying electronic prerequisite, the s hole in the XB donor, have been the subject of extensive theoretical studies. 7–9] Most recently, the attractive nature of XB between 1-iodoperfluoroalkanes and various donors has also been demonstrated and quantified in solution studies. Novel inhibitors of human Cathepsin L (hCatL) were discovered which bind covalently to the side chain of the catalytic Cys25 residue in the S1 pocket under formation of thioimidates, which are stabilized by the oxyanion hole of the protease. These ligands form hydrogen bonds to the backbone NH and C=O groups of Gly68 and Asp162, respectively, and fill the S2 and S3 pockets, thereby interacting with the enzyme through multiple lipophilic contacts. During the course of this research, we obtained an indication of an XB contact between a 4-chlorophenyl moiety of a ligand, whose binding affinity was enhanced by a factor of 13 compared to the unsubstituted phenyl derivative, and the backbone C=O group of Gly61 in the S3 pocket (Figure 1). This finding stimulated the prepa-

Insight into steroid scaffold formation from the structure of human oxidosqualene cyclase

Abstract: In higher organisms the formation of the steroid scaffold is catalysed exclusively by the membrane-bound oxidosqualene cyclase (OSC; lanosterol synthase). In a highly selective cyclization reaction OSC forms lanosterol with seven chiral centres starting from the linear substrate 2,3-oxidosqualene. Valuable data on the mechanism of the complex cyclization cascade have been collected during the past 50 years using suicide inhibitors, mutagenesis studies and homology modelling. Nevertheless it is still not fully understood how the enzyme catalyses the reaction. Because of the decisive role of OSC in cholesterol biosynthesis it represents a target for the discovery of novel anticholesteraemic drugs that could complement the widely used statins. Here we present two crystal structures of the human membrane protein OSC: the target protein with an inhibitor that showed cholesterol lowering in vivo opens the way for the structure-based design of new OSC inhibitors. The complex with the reaction product lanosterol gives a clear picture of the way in which the enzyme achieves product specificity in this highly exothermic cyclization reaction.

Fluorine in Pharmaceuticals: Looking Beyond Intuition.

Abstract: Fluorine substituents have become a widespread and important drug component, their introduction facilitated by the development of safe and selective fluorinating agents. Organofluorine affects nearly all physical and adsorption, distribution, metabolism, and excretion properties of a lead compound. Its inductive effects are relatively well understood, enhancing bioavailability, for example, by reducing the basicity of neighboring amines. In contrast, exploration of the specific influence of carbon-fluorine single bonds on docking interactions, whether through direct contact with the protein or through stereoelectronic effects on molecular conformation of the drug, has only recently begun. Here, we review experimental progress in this vein and add complementary analysis based on comprehensive searches in the Cambridge Structural Database and the Protein Data Bank.

Extra Precision Glide: Docking and Scoring Incorporating a Model of Hydrophobic Enclosure for Protein-Ligand Complexes

Abstract: A novel scoring function to estimate protein-ligand binding affinities has been developed and implemented as the Glide 4.0 XP scoring function and docking protocol. In addition to unique water desolvation energy terms, protein-ligand structural motifs leading to enhanced binding affinity are included: (1) hydrophobic enclosure where groups of lipophilic ligand atoms are enclosed on opposite faces by lipophilic protein atoms, (2) neutral-neutral single or correlated hydrogen bonds in a hydrophobically enclosed environment, and (3) five categories of charged-charged hydrogen bonds. The XP scoring function and docking protocol have been developed to reproduce experimental binding affinities for a set of 198 complexes (RMSDs of 2.26 and 1.73 kcal/mol over all and well-docked ligands, respectively) and to yield quality enrichments for a set of fifteen screens of pharmaceutical importance. Enrichment results demonstrate the importance of the novel XP molecular recognition and water scoring in separating active and inactive ligands and avoiding false positives.

The Halogen Bond

Abstract: The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.