Structural versatility of bovine ribonuclease A. Distinct conformers of trimeric and tetrameric aggregates of the enzyme.
Lyophilization of bovine ribonuclease A (RNase A; Sigma, type XII-A) from 40% acetic acid solutions leads to the formation of approximately 14 aggregated species that can be separated by ion-exchange chromatography. Several aggregates were identified, including two variously deamidated dimeric subspecies, two distinct trimeric and two distinct tetrameric RNase A conformers, besides the two forms of dimer characterized previously [Gotte, G. & Libonati, M. (1998) Two different forms of aggregated dimers of ribonuclease A. Biochim. Biophys. Acta 1386, 106-112]. We also have possible evidence for the existence of two forms of pentameric RNase A. The two forms of trimers and tetramers are characterized by: (a) slightly different gel filtration patterns; (b) different retention times in ion-exchange chromatography; and (c) different mobilities in cathodic gel electrophoresis under nondenaturing conditions. Therefore, they appear to have distinct structural organizations responsible for a different availability of their positively charged amino acid residues. All RNase A oligomers, in particular the two distinct trimeric and tetrameric conformers, degrade poly(A).poly(U), viral double-stranded RNA and polyadenylate with a catalytic efficiency that is in general higher for the more basic species. On the contrary, the activity of the RNase A oligomers, from dimer to pentamer, on yeast RNA and poly(C) (Kunitz assay) is lower than that of monomeric RNase A.
Gotte
G
G
Dipartimento di Scienze Neurologiche e della Visione, Sezione di Chimica Biologica, Facoltà di Medicina e Chirurgia, Università di Verona, Italy.
Bertoldi
M
M
Libonati
M
M
D000818:Animals; D002417:Cattle; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003432:Cross-Linking Reagents; D004120:Dimethyl Suberimidate; D004591:Electrophoresis, Polyacrylamide Gel; D008970:Molecular Weight; D010179:Pancreas / Q000201:enzymology; D011063:Poly A-U / Q000378:metabolism; D011487:Protein Conformation; D012330:RNA, Double-Stranded / Q000378:metabolism; D012259:Ribonuclease, Pancreatic / Q000737:chemistry*
D003432:Cross-Linking Reagents; D012330:RNA, Double-Stranded; D011063:Poly A-U; D004120:Dimethyl Suberimidate; D012259:Ribonuclease, Pancreatic