A conserved asparagine makes an essential contact to an RNA adenosine or cytidine.

Abstract Post-transriptional regulation of yeast ribosomal protein L30, RPL30, requires the formation of a complex comprised of RPL30 and its RNA transcript [J. Vilardell and J. R. Warner, Genes & Dev. 8, 211-220 (1994)]. Mutational analysis of both the RNA and the protein reveals that an asparagine-adenosine contact is important. Replacement of the asparagine by alanine weakens binding dramatically, but substitution of the adenosine by cytidine or guanosine slightly increases or decreases respective binding affinities for RPL30. The structure of the complex has been solved by NMR and shows a conserved asparagine in position to form two hydrogen bonds with adenosine's Watson-Crick face [H. Mao, S. A. White and J. R. Williamson, Nat. Struct. Biol. 6, 1139-1147 (1999)]. Asparagine is necessary for this interaction but relatively small differences in binding affinity are measured for three different nucleotides.