RNaseA Nobel Prizes: Difference between revisions

Interatomic interactions, delegated by the amino acid sequence, are responsible for formation of a protein's 3D structure [http://en.wikipedia.org/wiki/Protein_folding].  Several of these interactions have been identified by the use of site directed mutagenesis to wildtype RNase A and subsequent comparison of the crystal structure to the wildtype. Although RNase A has 105 possible disulfide bond pairings, only one set of four bonds occurs. This unique observation leads to the "thermodynamic hypothesis", that a protein's native state is determined by the thermodynamic favorability of the whole system; thus the tertiary structure must be predetermined by intramolecular interactions within the amino acid sequence.<ref>PMID: 4124164</ref> Since thermodynamic stability of a protein is affected by the environment's temperature, pH, and ionic strength, among other factors, the protein structure can only exist under physiological conditions. Today, the correlation between the amino acid sequence and the tertiary structure of RNase A continues to serve as a model for protein folding. Among the most important attributes of this model are noncovalent interactions, proline conformation, and disulfide bonding <ref name = 'Lehninger'>'Lehninger A., Nelson D.N, & Cox M.M. (2008) Lehninger Principles of Biochemistry. W. H. Freeman, fifth edition.' </ref>.

[[Image:13027382714469.png|thumb|280px|left|Semisynthetic RNase A. The synthetic peptide analog, RNase 111-118, is colored according to hydrophilicity. Yellow areas are comprised of hydrophobic residues. Red and brown segments are negatively and positively charged residues, respectively.]]The peptide synthesis of non-natural and non-coded proteins allowed scientists to analyze the mechanism and structure-activity relationships of classical enzyme molecules that were not accessible by traditional biomedical methods. These syntheses, though, were both difficult and time consuming, and advances in technique developed slowly<ref name = 'Merrifield'>Merrifield B. "Solid Phase Synthesis", Nobel Lecture, 8 December, 1984.</ref>. At the beginning of the twentieth century, Emil Fischer performed the first synthesis of a peptide, but it was not until 1953 that the first peptide hormone was synthesized by Du Vigneaud<ref name="Merrifield" />. The development of solid phase synthesis by Bruce Merrifield was a radical departure from traditional methods of bio-molecular synthesis that greatly increased efficiency. His method made possible the syntheses of much larger and more complex molecules; however, solid phase synthesis was not fully embraced until he demonstrated its full ability with the <scene name='Sandbox_Reserved_198/Fully_synthetic/2' target='1'>complete synthesis of Ribonuclease A</scene>. This milestone synthesis and subsequent semisynthetic syntheses of enzymes including <scene name='Sandbox_Reserved_198/Semisynthetic_rnase_a/1' target='1'>semisynthetic RNase A</scene> enriched the hypothesis that the amino acid sequence of a protein contains all necessary information to direct the formation of a fully active enzyme and, additionally, that an enzyme demonstrating the catalytic capacity and specificity of a naturally produced enzyme can be made in laboratory<ref name="Merrifield" /><ref name ='Martin'>PMID: 3680234</ref><ref name ='Boerema'>PMID: 17610259</ref>.