Practice question

tRNAPyl is unusual tRNA encoded by pylT with small D-loop, extended anticodon stem, and CUA anticodon complementary to amber UAG. Substrate for class IIc pyrrolysyl-tRNA synthetase, identity lies in acceptor stem not anticodon, permitting suppression. tRNAPyl lacks many canonical modifications yet efficiently aminoacylated and delivered by EF-Tu variant. Structural studies show elongated variable loop altering elbow angle influencing ribosome kinetics. Its orthogonal nature enables amber suppression technology widely exploited for site-specific noncanonical amino acid incorporation in synthetic biology, expanding protein engineering beyond natural twenty residues effectively.