Terminal tetraloops consisting of GNRA sequences are often found in biologi
cally active large RNAs. The loops appear to contribute towards the organiz
ation of higher order RNA structures by forming specific tertiary interacti
ons with their receptors. Group IC3 introns which possess a GAAA loop in th
e. L2 region often have a phylogenetically conserved motif in their P8 doma
ins. In this report, we show that this, conserved motif stands as a new cla
ss of receptor that distinguishes the sequences of GNRA loops less stringen
tly than previously known receptors. The motif can functionally substitute
an 11 nt motif receptor in the Tetrahymena ribozyme. Its structural and fun
ctional similarity to one class of synthetic receptors obtained from in vit
ro selection is observed.