Thermodynamics of core hydrophobicity and packing in the hyperthermophile proteins Sac7d and Sso7d.


Abstract

The influence of core hydrophobicity and packing on the structure and stability of the hyperthermophile proteins Sac7d and Sso7d have been studied by calorimetry, circular dichroism, and NMR. Valine 30 is positioned in Sac7d to allow a cavity-filling Val --> Ile substitution which occurs naturally in the homologous more thermostable Sso7d. The cavity-filling mutation in Sac7d has been characterized and compared to the reciprocal Ile --> Val mutation in Sso7d. A detailed analysis of the stability of the proteins was obtained by globally fitting the variation of DSC parameters and circular dichroism intensities as a function of temperature (0-100 degrees C), salt (0-0.3 M), and pH (0-8). A global analysis over such a range of conditions permitted an unusually precise measure of the thermodynamic parameters, as well as the separation of the thermodynamics of the intrinsic unfolding reaction from the linked effects of protonation and chloride binding associated with acid-induced folding. The results indicate differences in the energetics of unfolding Sac7d and Sso7d that would not be apparent from an analysis of DSC data alone using conventional methods. The sign and magnitude of the changes in DeltaG, DeltaH, TDeltaS, and DeltaC(P) of unfolding resulting from core Ile/Val substitutions in the two proteins were consistent with differences in hydrophobicity of Val and Ile and negligible changes in packing (van der Waals) interactions. The benefit of increased hydrophobicity of the core increased with temperature, with maximal effect around 116 degrees C. Increased hydrophobicity of the core achieved not only an increase in the free energy of unfolding, but also a lateral shift of the temperature of maximal stability to higher temperature. Study holds ProTherm entries: 16987, 16988, 16989, 16990, 16991, 16992 Extra Details: hydrophobicity; packing; hyperthermophile; cavity-filling

Submission Details

ID: tgi4tcAo

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:48 p.m.

Version: 1

Publication Details
Clark AT;McCrary BS;Edmondson SP;Shriver JW,Biochemistry (2004) Thermodynamics of core hydrophobicity and packing in the hyperthermophile proteins Sac7d and Sso7d. PMID:15005619
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P
 

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)


Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 DNA-binding protein 7d P39476 DN7D_SACS2
100.0 DNA-binding protein 7a P61991 DN7A_SACS2
100.0 DNA-binding protein 7a P61990 DN7A_SACSH
100.0 DNA-binding protein 7a D2PHL8 DN7A_SULID
96.9 DNA-binding protein 7d O59632 DN7B_SACSH
98.4 DNA-binding protein 7a F0NJT3 DN7B_SULIH
93.2 DNA-binding protein 7a Q96X56 DN7_SULTO
100.0 DNA-binding protein 7d P13123 DN7D_SULAC
92.3 DNA-binding protein 7d P13125 DN7E_SULAC
91.4 DNA-binding protein 7d F4B9I5 DN7B_ACIHW
92.9 DNA-binding protein 7d F4B8X5 DN7C_ACIHW