Ribosome display
Encyclopedia
Ribosome display is a technique used to perform in vitro protein
evolution to create proteins that can bind to a desired ligand
. The process results in translated proteins that are associated with their mRNA progenitor which is used, as a complex, to bind to an immobilized ligand in a selection step. The mRNA-protein hybrids that bind well are then reverse transcribed
to cDNA and their sequence amplified via PCR. The end result is a nucleotide
sequence that can be used to create tightly binding proteins.
During the subsequent binding, or panning, stages, the complex is introduced to surface-bound ligand. This can be accomplished several ways, for example using an affinity chromatography
column with a resin bed containing ligand, a 96-well plate with immobilized surface-bound ligand, or magnetic beads that have been coated with ligand. The complexes that bind well are immobilized. Subsequent elution of the binders via high salt concentrations, chelating agents, or mobile ligands which complex with the binding motif of the protein allow dissociation of the mRNA. The mRNA can then be reverse transcribed back into cDNA, undergo mutagenesis
, and iteratively fed into the process with greater selective pressure to isolate even better binders.
/peptide bead/multiple-well sequence separation that is common in assays involving nucleotide hybridization and provides a ready way to amplify the proteins that do bind without decrypting the sequence until necessary. At the same time, this method relies on generating large, concentrated pools of sequence diversity without gaps and keeping these sequences from degrading, hybridizing, and reacting with each other in ways that would create sequence-space gaps.
Competing methods for protein evolution in vitro are phage display
, yeast display
, bacterial display
, and mRNA display
. As it is performed entirely in vitro, there are two main advantages over other selection technologies. First, the diversity of the library is not limited by the transformation efficiency of bacterial cells, but only by the number of ribosomes and different mRNA molecules present in the test tube. Second, random mutations can be introduced easily after each selection round, as no library must be transformed after any diversification step. This allows facile directed evolution of binding proteins over several generations.
A prerequisite for the selection of proteins from libraries is the coupling of genotype (RNA, DNA) and phenotype (protein). In ribosome display, this link is accomplished during in vitro translation by stabilizing the complex consisting of the ribosome, the mRNA and the nascent, correctly folded polypeptide. The ribosomal complexes are allowed to bind to surface-immobilized target. Whereas non-bound complexes are washed away, mRNA of the complexes displaying a binding polypeptide can be recovered, and thus, the genetic information of the binding polypeptides is available for analysis.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
evolution to create proteins that can bind to a desired ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
. The process results in translated proteins that are associated with their mRNA progenitor which is used, as a complex, to bind to an immobilized ligand in a selection step. The mRNA-protein hybrids that bind well are then reverse transcribed
Reverse transcriptase
In the fields of molecular biology and biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into single-stranded DNA. It also helps in the formation of a double helix DNA once the RNA has been reverse...
to cDNA and their sequence amplified via PCR. The end result is a nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
sequence that can be used to create tightly binding proteins.
Ribosome display process
Ribosome display either begins with a DNA sequence or naive library of sequences coding for a specific protein. The sequence is transcribed, and then translated in vitro into protein. However, the DNA library coding for a particular library of binding proteins is genetically fused to a spacer sequence lacking a stop codon. This spacer sequence, when translated, is still attached to the peptidyl tRNA and occupies the ribosomal tunnel, and thus allows the protein of interest to protrude out of the ribosome and fold. What results is a complex of mRNA, ribosome, and protein which can bind to surface-bound ligand. This complex is stabilized with the lowering of temperature and the addition of cations such as Mg2+.During the subsequent binding, or panning, stages, the complex is introduced to surface-bound ligand. This can be accomplished several ways, for example using an affinity chromatography
Affinity chromatography
Affinity chromatography is a method of separating biochemical mixtures and based on a highly specific interaction such as that between antigen and antibody, enzyme and substrate, or receptor and ligand.-Uses:Affinity chromatography can be used to:...
column with a resin bed containing ligand, a 96-well plate with immobilized surface-bound ligand, or magnetic beads that have been coated with ligand. The complexes that bind well are immobilized. Subsequent elution of the binders via high salt concentrations, chelating agents, or mobile ligands which complex with the binding motif of the protein allow dissociation of the mRNA. The mRNA can then be reverse transcribed back into cDNA, undergo mutagenesis
Mutagenesis
Mutagenesis is a process by which the genetic information of an organism is changed in a stable manner, resulting in a mutation. It may occur spontaneously in nature, or as a result of exposure to mutagens. It can also be achieved experimentally using laboratory procedures...
, and iteratively fed into the process with greater selective pressure to isolate even better binders.
Advantages of ribosome display
By having the protein progenitor attached to the complex, the processes of ribosome display skips the microarrayMicroarray
A microarray is a multiplex lab-on-a-chip. It is a 2D array on a solid substrate that assays large amounts of biological material using high-throughput screening methods.Types of microarrays include:...
/peptide bead/multiple-well sequence separation that is common in assays involving nucleotide hybridization and provides a ready way to amplify the proteins that do bind without decrypting the sequence until necessary. At the same time, this method relies on generating large, concentrated pools of sequence diversity without gaps and keeping these sequences from degrading, hybridizing, and reacting with each other in ways that would create sequence-space gaps.
Competing methods for protein evolution in vitro are phage display
Phage display
Phage display is a method for the study of protein–protein, protein–peptide, and protein–DNA interactions that uses bacteriophages to connect proteins with the genetic information that encodes them. Phage Display was originally invented by George P...
, yeast display
Yeast display
Yeast display is a technique used in the field of protein engineering. The yeast display technique was first published by the laboratory of Professor K. Dane Wittrup. The technology was sold to Abbott Laboratories in 2001....
, bacterial display
Bacterial display
Bacterial display is a protein engineering technique used for in vitro protein evolution...
, and mRNA display
MRNA display
mRNA display is a display technique used for in vitro protein, and/or peptide evolution to create molecules that can bind to a desired target. The process results in translated peptides or proteins that are associated with their mRNA progenitor via a puromycin linkage. The complex then binds to...
. As it is performed entirely in vitro, there are two main advantages over other selection technologies. First, the diversity of the library is not limited by the transformation efficiency of bacterial cells, but only by the number of ribosomes and different mRNA molecules present in the test tube. Second, random mutations can be introduced easily after each selection round, as no library must be transformed after any diversification step. This allows facile directed evolution of binding proteins over several generations.
A prerequisite for the selection of proteins from libraries is the coupling of genotype (RNA, DNA) and phenotype (protein). In ribosome display, this link is accomplished during in vitro translation by stabilizing the complex consisting of the ribosome, the mRNA and the nascent, correctly folded polypeptide. The ribosomal complexes are allowed to bind to surface-immobilized target. Whereas non-bound complexes are washed away, mRNA of the complexes displaying a binding polypeptide can be recovered, and thus, the genetic information of the binding polypeptides is available for analysis.