If space is provided, bulky modification on the rim of Azurin's β‐barrel results in folded protein

FEBS Letters

Pozdnyakova, Irina¹  Wittung-Stafshede, Pernilla¹ 

[1]Department of Chemistry, Tulane University, 6832 St. Charles Avenue, New Orleans, LA 70118-5698, USA

关键词: Protein folding;    Azurin;    Thermal denaturation;    Differential scanning calorimetry;    Cysteine oxidation;    β-barrel stability;    GuHCl;    guanidine hydrochloride;    DSC;    differential scanning calorimetry;    CD;    circular dichroism;    Tm;    midpoint of thermal transition;   

DOI  :  10.1016/S0014-5793(02)03505-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Pseudomonas aeruginosa azurin is a blue-copper protein with a β-barrel fold. Here we report that, at conditions where thermal unfolding of apo-azurin is reversible, the reaction occurs in a single step with a transition midpoint (T _m) of 69°C (pH 7). The active-site mutation His117Gly creates a cavity in the β-barrel near the surface but does not perturb the overall fold (T _m of 64°C, pH 7). Oxidation of the active-site cysteine (Cysteine-112) in wild-type azurin, which occurs readily at higher temperatures, results in a modified protein that cannot adopt a native-like structure. In sharp contrast, Cysteine-112 oxidation in His117Gly azurin yields a modified apo-azurin that appears folded and displays cooperative, reversible unfolding (T _m∼55°C, pH 7). We conclude that azurin's β-barrel is a rigid structural element that constrains the structure of its surface; a bulky modification can only be accommodated if complementary space is provided.

【 授权许可】

Unknown