Structural Stability Comparisons Between Natural and Engineered Group II Chaperonins: Are Crenarchaeal “Heat Shock” Proteins Also “pH Shock” Resistant?

Authors

• Mercede Furr, University of Arkansas, Fayetteville
• Shadi A. Badiee, University of Arkansas, FayettevilleFollow
• Sreenivasulu Basha, University of Arkansas, Fayetteville
• Shilpi Agarwal, University of Arkansas, Fayetteville
• Zeina Ismael Ibrahem Alraawi, University of Arkansas, FayettevilleFollow
• Sobroney Heng, University of California Merced, Merced
• Carson L. Stacy, University of Arkansas, Fayetteville
• Yeasin Ahmed, University of California Merced, Merced
• Mahmoud Moradi, University of Arkansas, Fayetteville
• Thallapuranam Krishnaswamy Suresh Kumar, University of Arkansas, FayettevilleFollow
• Ruben Michael Ceballos, University of California Merced

Document Type

Article

Publication Date

11-18-2024

Keywords

group II chaperonin; Sulfolobales; thermotolerance; acido-tolerance; protein stability; heat shock protein; molecular dynamics; intrinsic fluorescence; circular dichroism; HSP60

Abstract

Archaeal group II chaperonins, also known as heat shock proteins (HSPs), are abundantly expressed in Sulfolobales. HSPα and HSPβ gene expression is upregulated during thermal shock. HSPs form large 18-mer complexes that assist in folding nascent proteins and protecting resident proteins during thermal stress. Engineered HSPs have been designed for industrial applications. Since temperature flux in the geothermal habitats of Sulfolobales impacts intracellular temperature, it follows that HSPs have developed thermotolerance. However, despite the low pH (i.e., pH < 4) typical for these habitats, intracellular pH in Sulfolobales is maintained at ~6.5. Therefore, it is not presumed that HSPs have evolved acid-tolerance. To test tolerance to low pH, HSPs were studied at various pH and temperature values. Both circular dichroism and intrinsic fluorescence indicate that HSPα and HSPβ retain structural integrity at neutral pH over a wide range of temperatures. Structural integrity is compromised for all HSPs at ultra-low pH (e.g., pH 2). Secondary structures in HSPs are resilient under mildly acidic conditions (pH 4) but Anilino naphthalene 8-sulfonate binding shows shifts in tertiary structure at lower pH. Trypsin digestion shows that the HSPβ-coh backbone is the most flexible and HSPβ is the most resilient. Overall, results suggest that HSPα and HSPβ exhibit greater thermostability than HSPβ-coh and that there are limits to HSP acid-tolerance. Molecular dynamics (MD) simulations complement the wet lab data. Specifically, MD suggests that the HSPβ secondary structure is the most stable. Also, despite similarities in pH- and temperature-dependent behavior, there are clear differences in how each HSP subtype is perturbed.

Citation

Furr, M., Badiee, S. A., Basha, S., Agrawal, S., Alraawi, Z., Heng, S., Stacy, C., Ahmed, Y., Moradi, M., Kumar, T. K. S., & Ceballos, R. M. (2024). Structural Stability Comparisons Between Natural and Engineered Group II Chaperonins: Are Crenarchaeal “Heat Shock” Proteins Also “pH Shock” Resistant? Microorganisms, 12(11), 2348. https://doi.org/10.3390/microorganisms12112348

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