Project description:S-adenosylmethionine-dependent methyltransferases are involved in countless biological processes, including signal transduction, epigenetics, natural product biosynthesis, and detoxification. Only a handful of carboxylate methyltransferases have evolved to participate in amide bond formation. In this report we show that enzyme-catalyzed F-methylation of carboxylate substrates produces F-methyl esters that readily react with N- or S-nucleophiles under physiological conditions. We demonstrate the applicability of this approach to the synthesis of small amides, hydroxamates, and thioesters, as well as to site-specific protein modification and native chemical ligation.
Project description:Transpeptidase-catalyzed protein and peptide modifications have been widely utilized for generating conjugates of interest for biological investigation or therapeutic applications. However, all known transpeptidases are constrained to ligating in the N-to-C orientation, limiting the scope of attainable products. Here, we report that an engineered asparaginyl ligase accepts diverse incoming nucleophile substrate mimetics, particularly when a means of selectively quenching the reactivity of byproducts released from the recognition sequence is employed. In addition to directly catalyzing formation of l-/d- or α-/β-amino acid junctions, we find C-terminal Leu-ethylenediamine (Leu-Eda) motifs to be bona fide mimetics of native N-terminal Gly-Leu sequences. Appending a C-terminal Leu-Eda to synthetic peptides or, via an intein-splicing approach, to recombinant proteins enables direct transpeptidase-catalyzed C-to-C ligations. This work significantly expands the synthetic scope of enzyme-catalyzed protein transpeptidation reactions.
Project description:Protein synthesis and semisynthesis offer immense promise for life sciences and have impacted pharmaceutical innovation. The absence of a generally applicable method for traceless peptide conjugation with a flexible choice of junction sites remains a bottleneck for accessing many important synthetic targets, however. Here we introduce the PALME (protein activation and ligation with multiple enzymes) platform designed for sequence-unconstrained synthesis and modification of biomacromolecules. The upstream activating modules accept and process easily accessible synthetic peptides and recombinant proteins, avoiding the challenges associated with preparation and manipulation of activated peptide substrates. Cooperatively, the downstream coupling module provides comprehensive solutions for sequential peptide condensation, cyclization and protein N/C-terminal or internal functionalization. The practical utility of this methodology is demonstrated by synthesizing a series of bioactive targets ranging from pharmaceutical ingredients to synthetically challenging proteins. The modular PALME platform exhibits unprecedentedly broad accessibility for traceless protein synthesis and functionalization, and holds enormous potential to extend the scope of protein chemistry and synthetic biology.
Project description:Enzymatic ligation is a popular method in DNA nanotechnology for structural enforcement. When employed as stability switch for chosen components, ligation can be applied to induce DNA nanostructure reconfiguration. In this study, we investigate the reinforcement effect of ligation on addressable DNA nanostructures assembled entirely from short synthetic strands as the basis of structural reconfiguration. A careful calibration of ligation efficiency is performed on structures with programmable nicks. Systematic investigation using comparative agarose gel electrophoresis enables quantitative assessment of enhanced survivability with ligation treatment on a number of unique structures. The solid ligation performance sets up the foundation for the ligation-based structural reconfiguration. With the capability of switching base pairing status between permanent and transient (ON and OFF) by a simple round of enzymatic treatment, ligation induced reconfiguration can be engineered for DNA nanostructures accordingly.
Project description:The non-enzymatic replication of the primordial genetic material is thought to have enabled the evolution of early forms of RNA-based life. However, the replication of oligonucleotides long enough to encode catalytic functions is problematic due to the low efficiency of template copying with mononucleotides. We show that template-directed ligation can assemble long RNAs from shorter oligonucleotides, which would be easier to replicate. The rate of ligation can be greatly enhanced by employing a 3'-amino group at the 3'-end of each oligonucleotide, in combination with an N-alkyl imidazole organocatalyst. These modifications enable the copying of RNA templates by the multistep ligation of tetranucleotide building blocks, as well as the assembly of long oligonucleotides using short splint oligonucleotides. We also demonstrate the formation of long oligonucleotides inside model prebiotic vesicles, which suggests a potential route to the assembly of artificial cells capable of evolution.
Project description:Neurexin and neuroligin are transmembrane adhesion proteins that play an important role in organizing the neuronal synaptic cleft. Our lab previously reported a method for imaging the trans-synaptic binding of neurexin and neuroligin called BLINC (Biotin Labeling of INtercellular Contacts). In BLINC, biotin ligase (BirA) is fused to one protein while its 15-amino acid acceptor peptide substrate (AP) is fused to the binding partner. When the two fusion proteins interact across cellular junctions, BirA catalyzes the site-specific biotinylation of AP, which can be read out by staining with streptavidin-fluorophore conjugates. Here, we report that BLINC in neurons cannot be reproduced using the reporter constructs and labeling protocol previously described. We uncover the technical reasons for the lack of reproducibilty and then re-design the BLINC reporters and labeling protocol to achieve neurexin-neuroligin BLINC imaging in neuron cultures. In addition, we introduce a new method, based on lipoic acid ligase instead of biotin ligase, to image trans-cellular neurexin-neuroligin interactions in human embryonic kidney cells and in neuron cultures. This method, called ID-PRIME for Interaction-Dependent PRobe Incorporation Mediated by Enzymes, is more robust than BLINC due to higher surface expression of lipoic acid ligase fusion constructs, gives stronger and more localized labeling, and is more versatile than BLINC in terms of signal readout. ID-PRIME expands the toolkit of methods available to study trans-cellular protein-protein interactions in living systems.
Project description:FastCloning, a paradigm shift in PCR cloning, has streamlined the process by eliminating laborious, multi-step traditional methods. This innovative technique, pioneered by Li et al. (2011), utilizes overlapping PCR primers and DpnI digestion for seamless integration of insert DNA into any desired vector position, regardless of restriction sites. This versatility makes FastCloning ideal for constructing fusion proteins, chimeric cDNAs, and manipulating genes with unparalleled ease. However, efficient primer design remains a critical hurdle, particularly for newcomers, as errors can lead to failed cloning attempts. To address this bottleneck, we present FastCloneAssist, a user-friendly Python program that automates FastCloning primer design with minimal user input. Users simply provide vector and insert sequences, along with the desired melting temperature (Tm), and FastCloneAssist provides best primer pairs after calculating optimal primer parameters for efficient PCR amplification and seamless DNA integration using established bioinformatics libraries. This open-source, freely available tool simplifies and accelerates cloning, making this powerful technique accessible to researchers of all levels and expediting scientific discovery.
Project description:The low thermal stability of DNA nanostructures is the major drawback in their practical applications. Most of the DNA nanotubes/tiles and the DNA origami structures melt below 60°C due to the presence of discontinuities in the phosphate backbone (i.e., nicks) of the staple strands. In molecular biology, enzymatic ligation is commonly used to seal the nicks in the duplex DNA. However, in DNA nanotechnology, the ligation procedures are neither optimized for the DNA origami nor routinely applied to link the nicks in it. Here, we report a detailed analysis and optimization of the conditions for the enzymatic ligation of the staple strands in four types of 2D square lattice DNA origami. Our results indicated that the ligation takes overnight, efficient at 37°C rather than the usual 16°C or room temperature, and typically requires much higher concentration of T4 DNA ligase. Under the optimized conditions, up to 10 staples ligation with a maximum ligation efficiency of 55% was achieved. Also, the ligation is found to increase the thermal stability of the origami as low as 5°C to as high as 20°C, depending on the structure. Further, our studies indicated that the ligation of the staple strands influences the globular structure/planarity of the DNA origami, and the origami is more compact when the staples are ligated. The globular structure of the native and ligated origami was also found to be altered dynamically and progressively upon ethidium bromide intercalation in a concentration-dependent manner.
Project description:Modern cells are complex chemical compartments tightly regulated by an underlying DNA-encoded program. Achieving a form of coupling between molecular content, chemical reactions, and chassis in synthetic compartments represents a key step to the assembly of evolvable protocells but remains challenging. Here, we design coacervate droplets that promote non-enzymatic oligonucleotide polymerization and that restructure as a result of the reaction dynamics. More specifically, we rationally exploit complexation between end-reactive oligonucleotides able to stack into long physical polymers and a cationic azobenzene photoswitch to produce three different phases-soft solids, liquid crystalline or isotropic coacervates droplets-each of them having a different impact on the reaction efficiency. Dynamical modulation of coacervate assembly and dissolution via trans-cis azobenzene photo-isomerization is used to demonstrate cycles of light-actuated oligonucleotide ligation. Remarkably, changes in the population of polynucleotides during polymerization induce phase transitions due to length-based DNA self-sorting to produce multiphase coacervates. Overall, by combining a tight reaction-structure coupling and environmental responsiveness, our reactive coacervates provide a general route to the non-enzymatic synthesis of polynucleotides and pave the way to the emergence of a primitive compartment-content coupling in membrane-free protocells.