Auburndale, Massachusetts, United States
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Apply below for Scientist and Lab Head Senior Principal Scientist positions to support in vitro antibody discovery in LMR US at Sanofi…
Apply below for Scientist and Lab Head Senior Principal Scientist positions to support in vitro antibody discovery in LMR US at Sanofi…
Liked by Nikolai Suslov
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Excited to share that I will be speaking at the 8th CDD for Biologics Summit’ this October (24-26)! Check out the complete event guide…
Excited to share that I will be speaking at the 8th CDD for Biologics Summit’ this October (24-26)! Check out the complete event guide…
Liked by Nikolai Suslov
Experience & Education
Publications
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Structural Basis for Substrate Helix Remodeling and Cleavage Loop Activation in the Varkud Satellite Ribozyme
JACS
The Varkud satellite (VS) ribozyme catalyzes site-specific RNA cleavage and ligation reactions. Recognition of the substrate involves a kissing loop interaction between the substrate and the catalytic domain of the ribozyme, resulting in a rearrangement of the substrate helix register into a so-called "shifted" conformation that is critical for substrate binding and activation. We report a 3.3 Å crystal structure of the complete ribozyme that reveals the active, shifted conformation of the…
The Varkud satellite (VS) ribozyme catalyzes site-specific RNA cleavage and ligation reactions. Recognition of the substrate involves a kissing loop interaction between the substrate and the catalytic domain of the ribozyme, resulting in a rearrangement of the substrate helix register into a so-called "shifted" conformation that is critical for substrate binding and activation. We report a 3.3 Å crystal structure of the complete ribozyme that reveals the active, shifted conformation of the substrate, docked into the catalytic domain of the ribozyme. Comparison to previous NMR structures of isolated, inactive substrates provides a physical description of substrate remodeling, and implicates roles for tertiary interactions in catalytic activation of the cleavage loop. Similarities to the hairpin ribozyme cleavage loop activation suggest general strategies to enhance fidelity in RNA folding and ribozyme cleavage.
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Crystal structure of the Varkud satellite ribozyme
Nature Chemical Biology
The Varkud satellite (VS) ribozyme mediates rolling-circle replication of a plasmid found in the Neurospora mitochondrion. We report crystal structures of this ribozyme from Neurospora intermedia at 3.1 Å resolution, which revealed an intertwined dimer formed by an exchange of substrate helices. In each protomer, an arrangement of three-way helical junctions organizes seven helices into a global fold that creates a docking site for the substrate helix of the other protomer, resulting in the…
The Varkud satellite (VS) ribozyme mediates rolling-circle replication of a plasmid found in the Neurospora mitochondrion. We report crystal structures of this ribozyme from Neurospora intermedia at 3.1 Å resolution, which revealed an intertwined dimer formed by an exchange of substrate helices. In each protomer, an arrangement of three-way helical junctions organizes seven helices into a global fold that creates a docking site for the substrate helix of the other protomer, resulting in the formation of two active sites in trans. This mode of RNA−RNA association resembles the process of domain swapping in proteins and has implications for RNA regulation and evolution. Within each active site, adenine and guanine nucleobases abut the scissile phosphate, poised to serve direct roles in catalysis. Similarities to the active sites of the hairpin and hammerhead ribozymes highlight the functional importance of active-site features, underscore the ability of RNA to access functional architectures from distant regions of sequence space, and suggest convergent evolution.
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A G-quadruplex-containing RNA activates fluorescence in a GFP-like fluorophore
Nature Chemical Biology
Spinach is an in vitro–selected RNA aptamer that binds a GFP-like ligand and activates its green fluorescence. Spinach is thus an RNA analog of GFP and has potentially widespread applications for in vivo labeling and imaging. We used antibody-assisted crystallography to determine the structures of Spinach both with and without bound fluorophore at 2.2-Å and 2.4-Å resolution, respectively. Spinach RNA has an elongated structure containing two helical domains separated by an internal bulge that…
Spinach is an in vitro–selected RNA aptamer that binds a GFP-like ligand and activates its green fluorescence. Spinach is thus an RNA analog of GFP and has potentially widespread applications for in vivo labeling and imaging. We used antibody-assisted crystallography to determine the structures of Spinach both with and without bound fluorophore at 2.2-Å and 2.4-Å resolution, respectively. Spinach RNA has an elongated structure containing two helical domains separated by an internal bulge that folds into a G-quadruplex motif of unusual topology. The G-quadruplex motif and adjacent nucleotides comprise a partially preformed binding site for the fluorophore. The fluorophore binds in a planar conformation and makes extensive aromatic stacking and hydrogen bond interactions with the RNA. Our findings provide a foundation for structure-based engineering of new fluorophore-binding RNA aptamers.
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The mechanism of peptidyl transfer catalysis by the ribosome
Annual Reviews of Biochemistry
The ribosome catalyzes two fundamental biological reactions: peptidyl transfer, the formation of a peptide bond during protein synthesis, and peptidyl hydrolysis, the release of the complete protein from the peptidyl tRNA upon completion of translation. The ribosome is able to utilize and distinguish the two different nucleophiles for each reaction, the α-amine of the incoming aminoacyl tRNA versus the water molecule. The correct binding of substrates induces structural rearrangements of…
The ribosome catalyzes two fundamental biological reactions: peptidyl transfer, the formation of a peptide bond during protein synthesis, and peptidyl hydrolysis, the release of the complete protein from the peptidyl tRNA upon completion of translation. The ribosome is able to utilize and distinguish the two different nucleophiles for each reaction, the α-amine of the incoming aminoacyl tRNA versus the water molecule. The correct binding of substrates induces structural rearrangements of ribosomal active-site residues and the substrates themselves, resulting in an orientation suitable for catalysis. In addition, active-site residues appear to provide further assistance by ordering active-site water molecules and providing an electrostatic environment via a hydrogen network that stabilizes the reaction intermediates and possibly shuttles protons. Major questions remain concerning the timing, components, and mechanism of the proton transfer steps. This review summarizes the recent progress in structural, biochemical, and computational advances and presents the current mechanistic models for these two reactions.
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A portable RNA sequence whose recognition by a synthetic antibody facilitates structural determination.
Nature Structural and Molecular Biology
RNA crystallization and phasing represent major bottlenecks in RNA structure determination. Seeking to exploit antibody fragments as RNA crystallization chaperones, we have used an arginine-enriched synthetic Fab library displayed on phage to obtain Fabs against the class I ligase ribozyme. We solved the structure of a Fab-ligase complex at 3.1-Å resolution using molecular replacement with Fab coordinates, confirming the ribozyme architecture and revealing the chaperone's role in RNA…
RNA crystallization and phasing represent major bottlenecks in RNA structure determination. Seeking to exploit antibody fragments as RNA crystallization chaperones, we have used an arginine-enriched synthetic Fab library displayed on phage to obtain Fabs against the class I ligase ribozyme. We solved the structure of a Fab-ligase complex at 3.1-Å resolution using molecular replacement with Fab coordinates, confirming the ribozyme architecture and revealing the chaperone's role in RNA recognition and crystal contacts. The epitope resides in the GAAACAC sequence that caps the P5 helix, and this sequence retains high-affinity Fab binding within the context of other structured RNAs. This portable epitope provides a new RNA crystallization chaperone system that easily can be screened in parallel to the U1A RNA-binding protein, with the advantages of a smaller loop and Fabs' high molecular weight, large surface area and phasing power.
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