Preparation in vitro of a 2‐Thiocytidine‐Containing Yeast tRNAPhe‐A₇₃‐C₇₄‐s²C₇₅‐A₇₆ and Its Interaction with p‐Hydroxymercuribenzoate

2‐Thiocytidine (s 2 C) is incorporated into yeast tRNA phe ‐A 73 ‐C 74 by tRNA nucleotidyl transferase. This leads to the formation of tRNA Phe ‐A 73 ‐C 74 ‐s 2 C 75 , which can be further converted to tRNA Phe ‐A 73 ‐C 74 ‐s 2 C 75 ‐A 76 . tRNA Phe with the s 2 CMP‐containing 3′‐end can be aminoacylated with the corresponding synthetase, exhibiting the same K m ‐values and slightly lowered V compared with tRNA Phe ‐A 73 ‐C 74 ‐C 75 ‐A 76 . The s 2 CMP incorporated is a specific site for binding p ‐hydroxymercuribenzoate; formation of 1:1 complex with a dissociation constant K d = 8.7 μM was observed. The modified tRNA can be crystallized.