H-1-NMR AND PHOTO-CIDNP SPECTROSCOPIES SHOW A POSSIBLE ROLE FOR TRP(23) AND PHE(31) IN NUCLEIC-ACID BINDING BY P2 RIBONUCLEASE FROM THE ARCHAEON SULFOLOBUS-SOLFATARICUS

Investigations were performed on recombinant ribonuclease P2 from Sulfolobus solfataricus, previously cloned and expressed in Escherichia coli [Fusi, P., Grisa, M., Mombelli, E., Consonni, R., Tortora, P. and Vanoni, M. (1995) Gene 154, 99-103], MMR and photo-CIDNP spectroscopies showed that the enzyme possesses an aromatic cluster constisting of Phe(5), Tyr(7), Phe(31) and Tyr(33) while Trp(23) is fully exposed to solvent, Phe(31), Tyr(33) and Trp(23) located within a triple stranded antiparallel beta-sheet, each one being part of an amino acid stretch matching consensus sequences for RNA binding, Phe(31) and Trp(23) are exposed to and specifically interact with a flavin dye used as a model ligand, with a topology reminiscent of that found in several eubacterial and eukariotic RNA-binding proteins.