Equilibrium unfolding of a small bacterial cytochrome, cytochrome c 551 from Pseudomonas aeruginosa

FEBS Letters

Staniforth, Rosemary A¹  Bigotti, Maria Giulia¹  Travaglini Allocatelli, Carlo¹  Cutruzzolà, Francesca¹  Brunori, Maurizio¹  Arese, Marzia¹ 

[1] Istituto Pasteur – Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche `A. Rossi-Fanelli' and Centro di Biologia Molecolare del CNR, Università di Roma `La Sapienza', Piazzale A. Moro 5, 00185 Rome, Italy

关键词: Cytochrome c;    Protein folding;    Stability;    Protein engineering;    Gdn·HCl;    guanidine hydrochloride;    cyt c;    cytochrome c;    cyt c 551;    cytochrome c 551;    WT;    wild type;   

DOI  :  10.1016/S0014-5793(98)00256-7

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The unfolding of the small cytochrome c ₅₅₁ from the bacterium Pseudomonas aeruginosa has been characterized at equilibrium by circular dichroism (CD) and fluorescence spectroscopy. The process can be described by a two state mechanism and the thermodynamic stability of cytochrome c ₅₅₁ is found to be smaller than that of the larger horse cytochrome c (ΔG _w=−8.2 vs. −9.7 kcal/mol); we propose that this finding is related to the absence of an `omega' loop in the bacterial cytochrome. Cytochrome c ₅₅₁ loses most of its secondary structure at pH 1.5. The acid transition (pK _A≈2) is highly cooperative (n≥2); analysis of optical titrations and contact map suggests that (at least) His-16 (proximal Fe³⁺ ligand) and Glu-70 are both involved in the acid transition. The role of selected hydrophobic, electrostatic and conformational contributions to the overall stability has been investigated by protein engineering. The equilibrium characterization of wild-type and mutant cytochrome c ₅₅₁ supports the view that this small cytochrome is an interesting protein to analyze the thermodynamics and the kinetics of folding in comparison with the widely studied horse cytochrome c.

【 授权许可】

Unknown