Stability and folding of amphibian ribonuclease A superfamily members in comparison with mammalian homologues

Abstract

Comparative studies on homologous proteins can provide knowledge on how limited changes in the primary structure find their expression in large effects on catalytic activity, stability or the folding behavior. For more than half a century, members of the ribonuclease A superfamily have been the subject of a myriad of studies on protein folding and stability. Both the unfolding and refolding kinetics as well as the structure of several folding intermediates of ribonuclease A have been characterized in detail. Moreover, the RNA-degrading activity of these enzymes provides a basis for their cytotoxicity, which renders them potential tumor therapeutics. Because amphibian ribonuclease A homologues evade the human ribonuclease inhibitor, they emerged as particularly promising candidates. Interestingly, the amphibian ribonuclease A homologues investigated to date are more stable than the mammalian homologues. Nevertheless, despite the generation of numerous genetically engineered variants, knowledge of the folding of amphibian ribonuclease A homologues remains rather limited. An exception is onconase, a ribonuclease A homologue from Rana pipiens, which has been characterized in detail. This review summarizes the data on the unfolding and refolding kinetics and pathways, as well on the stability of amphibian ribonuclease A homologues compared with those of ribonuclease A, the best known member of this superfamily.

Fluorescence lifetime components reveal kinetic intermediate states upon equilibrium denaturation of carbonic anhydrase II

“…Experimentalists face such challenge rather frequently. For example, under equilibrium conditions lysozyme, apomyoglobin, ribonuclease A, barnase and some other proteins behave as two-state proteins, and kinetic experiments allow revealing intermediate states formed upon their folding [7][8][9][10][11][12][13]. The solution to this problem is to find an experimental method that is sensitive enough to distinguish between different intermediate states of the protein.…”

Differential Expression of Six Rnase2 and Three Rnase3 Paralogs Identified in Blunt Snout Bream in Response to Aeromonas hydrophila Infection

“…RnaseA has been widely studied in the context of biological activities, molecular evolution, structural function and physiological diseases in mammals [ 43 ], amphibians [ 44 ], primates [ 45 ], and teleosts [ 7 ]. Many members of the RnaseA superfamily have antibacterial and antiviral activities.…”

Biological Activities of Secretory RNases: Focus on Their Oligomerization to Design Antitumor Drugs

“…ANG is 123 AA residues long and is so called because of its active role in the new vessels formation, but it exerts ribonucleolytic activity against tRNAs as well (21–23). Again, other RNases belonging to non-mammalian species, such as birds or amphibians, are also known (24, 25). Among these RNases, the most studied are the 114 AA residues amphinase and, above all, the smallest variant called ranpirnase or P-30 protein, which is formed only by 104 AA residues (26, 27).…”

“…This aspect acquires increasing importance if we recall that RNases can often interact with a polymeric substrate and not only with short oligonucleotides (29). We also point out Arnold's quite interesting review in which the principal features of mammalian and amphibian RNases have been exhaustively compared (25).…”