The invention provides methods and compositions for a mutein aminoacyl-tRNA synthetase that preferentially charges a tRNA with a non-natural amino acid. Also provided are methods for incorporating the non-natural amino acids, pyridinyl-amino tetrazine amino acids, into a protein, and further conjugating a biologically active adduct to the pyridinyl-amino tetrazine.

The invention provides methods and compositions for a mutein aminoacyl-tRNA synthetase that preferentially charges a tRNA with a non-natural amino acid. Also provided are methods for incorporating the non-natural amino acid, para-methylazido-L-phenylalanine into a protein and further conjugating a biologically active adduct to the para-methylazido-L-phenylalanine.

Provided herein are modified amino acids comprising a tetrazine groups according to Formula I: polypeptides, antibodies, payloads and conjugates comprising these modified amino acid residues derived from the modified amino acids, and methods of producing the polypeptides, antibodies, payloads and conjugates comprising the modified amino acid residues. The polypeptides, antibodies, payloads and conjugates are useful in methods of treatment and prevention, methods of detection and methods of diagnosis.

##STR00001##

Thrombopoietic compositions are provided comprising tyrosyl tRNA synthetase polypeptides, including truncations and/or variants thereof. Also provided are methods of using such compositions in the treatment of conditions that benefit from increased thrombopoiesis, such as thrombocytopenia.

The present invention provides PEGylated tyrosyl-tRNA synthetase (YRS) polypeptides, compositions comprising the same, and methods of using such polypeptides and compositions for treating or diagnosing a variety of conditions. The PEGylated YRS polypeptides of the invention have improved controlled release properties, stability, half-life, and other pharmacokinetic properties compared to non-PEGylated YRS polypeptides.

Compositions of bacterial tyrosyl-tRNA synthetase mutants that enable site-specific incorporation of numerous unnatural amino acids into proteins expressed in eukaryotic cells or in engineered ATM E. coli and methods of use are described. Compositions of novel unnatural amino acids that can be incorporated using these mutant bacterial tyrosyl-tRNA synthetase are also described.

A method for one of altering and enhancing the stereospecificity of an enzyme comprising introducing a stereospecific editing domain into the enzyme.

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.

This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

An engineered tyrosyl-tRNA synthetase/tRNA pair that co-translationally incorporates O-sulfotyrosine in response to UAG codons in E. coli and mammalian cells is described herein. This platform enables recombinant expression of eukaryotic proteins homogeneously sulfated at chosen sites.