The invention relates to aminoacyl-tRNA synthetases that aminoacylate tRNA with 2-Aminoisobutyric acid (Aib), thus enabling the incorporation of the Aib into a growing polypeptide chain during translation, e.g. in eubacterial host cells such as E. coli. For example, but not limited to, the invention relates to new aminoacyl-tRNA synthetases and the uses hereof, as well as a method for producing polypeptides that contain one or more Aib.

Provided herein are methods for labeling the proteomes of cells, as well as methods for labeling proteins or populations of proteins produced by cells. In some embodiments, the methods comprise introducing variant aminoacyl-tRNA synthetases and noncanonical amino acids into cells. Also provided herein are polynucleotides encoding variant aminoacyl-tRNA synthetases that recognize noncanonical amino acids. The methods and compositions provided herein are useful for, among other things, identifying target cells and identifying biomarkers of interest.

The invention relates to a polypeptide comprising an amino acid having a cyclopropene group wherein said cyclopropene group is joined to the amino acid via a carbamate group. Suitably the cyclopropene group is a 1,3-disubstituted cyclopropene such as a 1,3-dimethylcyclopropene. Suitably the cyclopropene group is present as a residue of a lysine amino acid. The invention also relates to methods of making the polypeptides. The invention also relates to an amino acid comprising cyclopropene wherein said cyclopropene group is joined to the amino acid moiety via a carbamate group.

Provided are compositions comprising newly identified protein fragments of aminoacyl-tRNA synthetases, polynucleotides that encode them and complements thereof, related agents, and methods of use thereof in diagnostic, drug discovery, research, and therapeutic applications.

Compositions, systems, and methods for preparation of polypeptides having multiple iterations of non-standard amino acids are provided. The compositions and method can be used to produce recombinant proteins at a greater yield than the same or similar polypeptides made using conventional compositions, systems, and methods. Accordingly, in some embodiments, the polypeptides are ones that could not be made using conventional methods and reagents, or could not be made a sufficient yield or purity to serve a practical purpose using conventional methods and reagents. Polypeptides made using the disclosed compositions, systems, and methods are also provided.

Provided are compositions comprising newly identified protein fragments of aminoacyl-tRNA synthetases, polynucleotides that encode them and complements thereof, related agents, and methods of use thereof in diagnostic, drug discovery, research, and therapeutic applications.

Provided are compositions comprising newly identified protein fragments of aminoacyl-tRNA synthetases, polynucleotides that encode them and complements thereof, related agents, and methods of use thereof in diagnostic, drug discovery, research, and therapeutic applications.

Provided are compositions comprising newly identified protein fragments of aminoacyl-tRNA synthetases, polynucleotides that encode them and complements thereof, related agents, and methods of use thereof in diagnostic, drug discovery, research, and therapeutic applications.

The disclosure provides methods of making a protein having a desired non-standard amino acid incorporated at its N-terminus in a cell and methods of screening for an amino acyl tRNA synthetase variant that preferentially selects a non-standard amino acid against its standard amino acid counterpart or undesired non-standard amino acids for incorporation into a protein in a cell.

Provided are compositions comprising newly identified protein fragments of aminoacyl-tRNA synthetases, polynucleotides that encode them and complements thereof, related agents, and methods of use thereof in diagnostic, drug discovery, research, and therapeutic applications.