Posttranslational NH₂-Terminal Aminoacylation

This chapter presents an overview of posttranslational NH₂-terminal aminoacylation. Aminoacyl-tRNA protein transferases catalyze the addition of certain amino acids to the NH₂-terminus of specific proteins and peptides. These enzymes constitute one mechanism for the posttranslational modification of NH₂-termini and may contribute to the heterogeneity in NH₂-terminal residues, which has been observed in bulk proteins of both prokaryotes and eukaryotes. Modifications of the NH₂-terminus can be classified into three basic types: (1) cleavage reactions, in which a formyl, methionyl, or other residue is removed; (2) alteration reactions, in which it is converted to another type of molecule, such as an α-keto acid or a cyclized derivative; and (3) addition reactions, including acetylation, phosphorylation, and aminoacylation, in which small molecules are added to it. The chapter focuses on the biochemistry and physiological function of the reactions catalyzed by aminoacyl-tRNA protein transferases.