Functional contacts of a transfer RNA synthetase with 2'-hydroxyl groups in the RNA minor groove. |
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Authors: | K Musier-Forsyth P Schimmel |
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Affiliation: | Department of Biology, Massachusetts Institute of Technology, Cambridge 02139. |
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Abstract: | The functional analysis of determinants on RNA has been largely limited to molecules that contain naturally occurring ribonucleotides, so little is known about the role of 2'-hydroxyl groups in protein-RNA recognition. A single base pair (G3.U70) in the acceptor stem of tRNA(Ala) is the principal element for specific recognition by Escherichia coli alanine-tRNA synthetase. This tRNA synthetase aminoacylates small RNA helices that contain the G3.U70 base pair. Furthermore, removal of the G3 exocyclic 2-amino group that projects into the minor groove eliminates aminoacylation. This 2-amino group is flanked on either side by ribose 2'-hydroxyl groups that line the minor groove. Here we use chemical synthesis to construct 32 helices that make deoxy and O-methyl substitutions of individual and multiple 2'-hydroxyl groups near and beyond the G3.U70 base pair and find that functional 2'-hydroxyl contacts are clustered within a few ?ngstroms of the critical 2-amino group. These contacts are highly specific and make a thermodynamically significant contribution to RNA recognition. |
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