RNA



Molecular recognition of amino acids by RNA aptamers: The evolution into an L-tyrosine binder of a dopamine-binding RNA motif


CECILIA  MANNIRONI a1, CHIARA  SCERCH a1, PAOLO  FRUSCOLONI a1 and GLAUCO P.  TOCCHINI-VALENTINI a1c1
a1 Istituto di Biologia Cellulare, Consiglio Nazionale delle Ricerche, “Adriano Buzzati-Traverso” Campus, I-00016 Monterotondo Scalo, Rome, Italy

Abstract

We report the evolution of an RNA aptamer to change its binding specificity. RNA aptamers that bind the free amino acid tyrosine were in vitro selected from a degenerate pool derived from a previously selected dopamine aptamer. Three independent sequences bind tyrosine in solution, the winner of the selection binding with a dissociation constant of 35 [mu]M. Competitive affinity chromatography with tyrosine-related ligands indicated that the selected aptamers are highly L-stereo selective and also recognize L-tryptophan and L-dopa with similar affinity. The binding site was localized by sequence comparison, analysis of minimal boundaries, and structural probing upon ligand binding. Tyrosine-binding sites are characterized by the presence of both tyrosine (UAU and UAC) and termination (UAG and UAA) triplets.

(Received August 11 1999)
(Revised September 14 1999)
(Accepted January 26 2000)


Key Words: affinity chromatography; amino acid; RNA aptamers; selection-amplification.

Correspondence:
c1 Reprint requests to: Glauco P. Tocchini-Valentini, Istituto di Biologia Cellulare, CNR, Campus “A. Buzzati-Traverso”, Via E. Ramarini, 32, 00016 Monterotondo Scalo (Roma), Italy; e-mail: gtocchini@ibc.rm.cnr.it.