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Effect of urea and alkylureas on the stability and structural fluctuation of the M80-containing Ω-loop of horse cytochrome c.

DIR@IMTECH: CSIR-Institute of Microbial Technology

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Title Effect of urea and alkylureas on the stability and structural fluctuation of the M80-containing Ω-loop of horse cytochrome c.
 
Creator Kumar, Sandeep
Sharma, Deepak
Kumar, Rajesh
 
Subject QR Microbiology
 
Description The effect of denaturants on the structural fluctuation of M80-containing Ω-loop of ferrocytochrome c was determined by measuring the rate coefficient of CO-association with ferrocytochrome c under varying concentrations of urea and alkylureas (methylurea (MU), N,N'-dimethylurea (DMU), ethylurea (EU), tetramethylurea (TMU)) at pH7.0, 25°C. As denaturant concentration is increased within the subdenaturing limit, the CO-association reaction is decelerated indicating that subdenaturing concentrations of denaturant reduce the structural fluctuation of the Ω-loop. Structural fluctuation of the Ω-loop is reduced more for urea and least for TMU. Intermolecular docking between horse cytochrome c and denaturant molecule (urea, MU, DMU, EU and TMU) reveals that polyfunctional interactions between the denaturant and different groups of Ω-loop and other part of protein decrease with an increase of alkyl group on urea molecule, which suggests that the decrease in the extent of restricted dynamics of Ω-loop with a corresponding increase of alkyl groups on urea molecule is due to the decrease of denaturant-mediated cross-linking interactions. These denaturant-mediated interactions are expected to reduce the conformational entropy of protein. Analysis of rate-temperature data shows a progressive decrease in conformational entropy of protein in the native to subdenaturing region. Thermodynamic analysis of denaturant (urea, MU, DMU, EU, TMU) effects on the thermal unfolding of ferrocytochrome c reveals that (i) thermodynamic stability of protein decreases with increasing concentration of denaturant or hydrophobicity of urea derivatives, (ii) water activity plays an important role in stabilization of ferrocytochrome c, and (iii) destabilization of ferrocytochrome c by denaturant occurs through the disturbance of hydrophobic interactions and hydrogen-bonding.
 
Publisher Elsevier Publisher
 
Date 2014-03
 
Type Article
PeerReviewed
 
Relation http://www.sciencedirect.com/science/article/pii/S1570963914000156
http://crdd.osdd.net/open/1708/
 
Identifier Kumar, Sandeep and Sharma, Deepak and Kumar, Rajesh (2014) Effect of urea and alkylureas on the stability and structural fluctuation of the M80-containing Ω-loop of horse cytochrome c. Biochimica et biophysica acta, 1844 (3). pp. 641-55. ISSN 0006-3002