Presented By: LSA Biophysics
Pre-Doctoral Student - Katherine Gentry and Brian Linhares
Katherine Gentry "Dynamic Interplay of Cytochrome P450 & Redox Partners" and Brian Linhares "Fragment-Based Identification and Optimization of Inhibitors Targeting BCL6-Co-Repressor Interactions.”
Katherine Gentry: "Dynamic Interplay of Cytochrome P450 & Redox Partners"
Abstract: Cytochrome P450s (cytP450s) are a ubiquitous superfamily of enzymes that play a vital role in the metabolism of many substrates including over 70% of the drugs on the market. For each turn of its catalytic cycle, cytP450 requires two electrons from its redox partners: Cytochrome P450 Reductase (CPR) and cytochrome b5 (cytb5). We are interested in how these proteins interact with each other specifically in the presence of lipid membrane mimetics and in the presence of various substrates. Here we use NMR spectroscopy and other biophysical tools to characterize the effect membrane has on the interaction between cytb5 and cytochrome c, a model for cytP450. Our findings reveal the importance of studying these membrane proteins in a biologically relevant membrane mimetic both structurally and kinetically. We have also begun work on understanding how CPR and cytb5 compete for binding to cytP450 and unravelling the structural and dynamic basis for this competition. Our data reveals how substrates can help to modulate the interaction between the two redox partners and cytP450, starting to define a complete picture of this trio of proteins.
and
Brian Linhares: “Fragment-based identification and optimization of inhibitors targeting BCL6-co-repressor interactions.”
Abstract: Constitutively overexpressed B-Cell Lymphoma protein 6 (BCL6) is an oncogenic driver in various subtypes of Diffuse Large B-Cell Lymphoma. In normal B-Cell physiology, BCL6 governs cell development and regulates affinity antibody maturation, through mediating the formation of transcription repression complexes. The N-terminal BTB domain of BCL6 (BCL6BTB) is responsible for dimerization and for recruitment of co-repressors, notably HDAC3-binding partner Silencing Mediator of Retinoic acid and Thyroid hormone (SMRT), via the Lateral Groove (LG), a unique structural motif of the BCL6-SMRT protein-protein binding interface. This site has therefore been promoted for pharmacological intervention, yet the development of potent, selective inhibitors with favorable drug-like properties has largely eluded campaigns to target BCL6. I will report the identification and optimization of a novel inhibitor scaffold of BCL6 BTB. Fragment-based screening identified a hit that binds at the LG, and structure determination of the fragment hit in complex with BCL6 BTB to high-resolution revealed the binding mode. Guided by the previously determined structure of BCL6BTB-SMRT BCL6 Binding Domain (SMRTBBD), structure-based drug design, in tandem with biophysical approaches, led an extensive investment in synthetic medicinal chemistry to target an adjacent pocket at the LG that is also occupied in BCL6BTB-SMRTBBD. Exploring substitutions to more fully occupy this pocket yielded small-molecule inhibitors with mid-micromolar affinity for BCL6BTB, which represents a 100-fold improvement in potency from the hit. As an inhibitor scaffold, our compounds may hold potential as chemical probes, and in scaffold hopping to aid in further inhibitor development
Abstract: Cytochrome P450s (cytP450s) are a ubiquitous superfamily of enzymes that play a vital role in the metabolism of many substrates including over 70% of the drugs on the market. For each turn of its catalytic cycle, cytP450 requires two electrons from its redox partners: Cytochrome P450 Reductase (CPR) and cytochrome b5 (cytb5). We are interested in how these proteins interact with each other specifically in the presence of lipid membrane mimetics and in the presence of various substrates. Here we use NMR spectroscopy and other biophysical tools to characterize the effect membrane has on the interaction between cytb5 and cytochrome c, a model for cytP450. Our findings reveal the importance of studying these membrane proteins in a biologically relevant membrane mimetic both structurally and kinetically. We have also begun work on understanding how CPR and cytb5 compete for binding to cytP450 and unravelling the structural and dynamic basis for this competition. Our data reveals how substrates can help to modulate the interaction between the two redox partners and cytP450, starting to define a complete picture of this trio of proteins.
and
Brian Linhares: “Fragment-based identification and optimization of inhibitors targeting BCL6-co-repressor interactions.”
Abstract: Constitutively overexpressed B-Cell Lymphoma protein 6 (BCL6) is an oncogenic driver in various subtypes of Diffuse Large B-Cell Lymphoma. In normal B-Cell physiology, BCL6 governs cell development and regulates affinity antibody maturation, through mediating the formation of transcription repression complexes. The N-terminal BTB domain of BCL6 (BCL6BTB) is responsible for dimerization and for recruitment of co-repressors, notably HDAC3-binding partner Silencing Mediator of Retinoic acid and Thyroid hormone (SMRT), via the Lateral Groove (LG), a unique structural motif of the BCL6-SMRT protein-protein binding interface. This site has therefore been promoted for pharmacological intervention, yet the development of potent, selective inhibitors with favorable drug-like properties has largely eluded campaigns to target BCL6. I will report the identification and optimization of a novel inhibitor scaffold of BCL6 BTB. Fragment-based screening identified a hit that binds at the LG, and structure determination of the fragment hit in complex with BCL6 BTB to high-resolution revealed the binding mode. Guided by the previously determined structure of BCL6BTB-SMRT BCL6 Binding Domain (SMRTBBD), structure-based drug design, in tandem with biophysical approaches, led an extensive investment in synthetic medicinal chemistry to target an adjacent pocket at the LG that is also occupied in BCL6BTB-SMRTBBD. Exploring substitutions to more fully occupy this pocket yielded small-molecule inhibitors with mid-micromolar affinity for BCL6BTB, which represents a 100-fold improvement in potency from the hit. As an inhibitor scaffold, our compounds may hold potential as chemical probes, and in scaffold hopping to aid in further inhibitor development
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