title: RNase A - tRNA binding alters protein conformation.
abstract: Bovine pancreatic ribonuclease A (RNase A) catalyzes the cleavage of P-O5' bonds in RNA on the 3' side of pyrimidine to form cyclic 2',5'-phosphates. Even though extensive structural information is available on RNase A complexes with mononucleotides and oligonucleotides, the interaction of RNase A with tRNA has not been fully investigated. We report the complexation of tRNA with RNase A in aqueous solution under physiological conditions, using a constant RNA concentration and various amounts of RNase A. Fourier transform infrared, UV-visible, and circular dichroism spectroscopic methods were used to determine the RNase binding mode, binding constant, sequence preference, and biopolymer secondary structural changes in the RNase-tRNA complexes. Spectroscopic results showed 2 major binding sites for RNase A on tRNA, with an overall binding constant of K = 4.0 x 105 (mol/L)-1. The 2 binding sites were located at the G-C base pairs and the backbone PO2 group. Protein-RNA interaction alters RNase secondary structure, with a major reduction in alpha helix and beta sheets and an increase in the turn and random coil structures, while tRNA remains in the A conformation upon protein interaction. No tRNA digestion was observed upon RNase A complexation.
authors.affiliation: Department of Chemistry-Biology, Université du Québec at Trois-Rivières, C.P. 500 Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: C N
authors.initials: CN
authors.lastname: N'soukpoé-Kossi
authors.forename: C
authors.initials: C
authors.lastname: Ragi
authors.forename: H A
authors.initials: HA
authors.lastname: Tajmir-Riahi
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002942:Circular Dichroism; D066298:In Vitro Techniques; D007700:Kinetics; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012331:RNA, Fungal / Q000737:chemistry / Q000378:metabolism; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism*; D012259:Ribonuclease, Pancreatic / Q000737:chemistry* / Q000378:metabolism*; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D012331:RNA, Fungal; D012343:RNA, Transfer; D012259:Ribonuclease, Pancreatic