Ribonuclease P2 from the thermophilic archaebacterium Sulfolobus solfataricus is a small protein (7 kDa) with a known three-dimensional structure. Inspection of the structure and molecular dynamics simulation reveal that three aromatic residues (Phe5, Phe31, and Tyr33) from the hydrophobic core have a strong van der Waals interaction energy. We studied the thermodynamics of the heat, cold, and pressure-induced protein conformational changes of the wild type and of the F31A and F31Y mutants by analyzing the protein UV absorbance in the fourth derivative mode. The wild-type protein was extremely stable under all conditions of temperature and pressure. Heat and cold denaturation of both mutants, as well as denaturation by pressure of the F31A mutant, led to significant blue shifts of the derivative spectrum, indicating increased solvent exposure of Tyr33. For the F31Y mutant, high pressure (400 MPa) protected the protein against thermal denaturation. This study, probing the properties of the hydrophobic aromatic core, complements a thermal unfolding study which probes the overall structural changes [Knapp, S., Karshikoff, A., Berndt, K. D., Christova, P., Atanasov, B., & Ladenstein, R. (1996) J. Mol. Biol. 264,1132-1144]. The differences observed in response to extremes of temperature, pressure, and pH may be rationalized by an unfolding mechanism involving larger parts of the peripheral protein while the integrity of the hydrophobic core is maintained. Study holds ProTherm entries: 8800, 8801 Extra Details: hydrophobic core; van der Waals interaction energy; pressure-induced,protein conformational changes; thermal unfolding; structural changes
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:36 p.m.
|Number of data points||4|
|Proteins||DNA-binding protein 7a ; DNA-binding protein 7a ; DNA-binding protein 7a|
|Assays/Quantities/Protocols||Experimental Assay: Tm pH:3.0 ; Experimental Assay: dHvH pH:3.0 ; Experimental Assay: Tm pH:7.4 ; Experimental Assay: dHvH pH:7.4|
|Libraries||Mutations for sequence ATVKFKYKGEEKQVDISKIKKVWRVGKMISFTYDEGGGKTGRGAVSEKDAPKELLQMLEKQK|