Structure of a mimic of aminoacylated tRNA determined by means of transferred NOE data

Abstract

Anthraniloyladenosine (Ant-Ado) serves as an analog for aminoacylated tRNA and is specifically recognized by bacterial elongation factor Tu (EF-Tu). In this compound, adenosine is esterified with anthranilic acid, which mimics an α-amino acid. The weak binding of Ant-Ado to the EF-Tu gives rise to transfer-NOE (TrNOE) signals from which the conformation of Ant-Ado in its protein-bound state can be deduced. To this end a full relaxation matrix approach was used with the R-factor as a target function. The position of the base was determined by a mapping procedure. Structures of ribose and anthranilic acid were obtained by simulated annealing. The nucleotide was found to be in 2′-endo puckering, with the base in an anti conformation. The anthranilic acid adopts a position in which an amino group is presented in a similar way as by phenylalanine in the crystal structure of the ternary complex EF-Tu·GPPNHP·Phe-tRNAPhe. © 1998 John Wiley & Sons, Ltd.