Table 2.

Progressive modifications of yeast tRNA^Cys (yCys01) and of human tRNA^Cys (hCys01) to generate yCys13 and hCys15

tRNA	15⋅48	13⋅22⋅46	47	21	32	37	Activity	DMS	KTX
eCys01	G⋅G	A⋅A⋅A	—	U	U	A	1.00	+	+
yCys01	G⋅C	C⋅G⋅G	U	A	U	A	0.01	−	−
yCys09	G⋅G	A⋅A⋅G	U	U	U	A	0.01	+
yCys10	G⋅G	A⋅A⋅A	U	U	U	A	0.02	+
yCys11	G⋅G	A⋅A⋅A	—	U	U	A	0.04	+
yCys13	G⋅G	A⋅A⋅A	—	A	U	A	0.28	+	+
hCys01	G⋅C	C⋅G⋅G	U	A	C	G	0.02	−	−
hCys05	G⋅G	A⋅A⋅G	U	U	C	G	0.001	+
hCys06	G⋅G	A⋅A⋅A	U	U	C	G	0.005	+
hCys07	G⋅G	A⋅A⋅A	—	U	C	G	0.08	+
hCys11	G⋅G	A⋅A⋅A	—	A	C	G	0.03	+	+
hCys12	G⋅G	A⋅A⋅A	—	U	U	A	0.97	+	+
hCys14	G⋅G	A⋅A⋅A	—	A	U	A	0.30
hCys15	G⋅G	A⋅A⋅A	—	U	C	A	1.71	+

Nucleotide sequences of E. coli tRNA^Cys (eCys01) and those of the yeast and human tRNA variants. Activities are indicated as relative k_cat/K_m to that of the eCys01 tRNA by the E. coli enzyme and were determined by measurements of k_cat and K_m. The average of the standard deviations is 5%. Deletion of nucleotide 47 is indicated by “—”, and chemical accessibility or inaccessibility to DMS and KTX (kethoxal) is indicated by “+” or “−”.