Mutations in the GTPase Center of Escherichia coli 23S rRNA Indicate Release Factor 2-Interactive Sites

Mutations in the GTPase center of Escherichia coli 23S rRNA were characterized in vivo as UGA-specific nonsense suppressors. Some site-directed mutations did not exhibit suppressor activity and were interspersed among suppressor mutations. Our results demonstrate the involvement of the two adjacent loops of this conserved rRNA structure in UGA-dependent translation termination and, taken with previous in vitro analyses and with consideration of the crystal structure of the GTPase center RNA, indicate that nucleotides 1067, 1093, 1094, and 1095 are sites of interaction with release factor 2.