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KMID : 0624620100430030176
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BMB Reports
2010 Volume.43 No. 3 p.176 ~ p.181
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Stabilization of the primary sigma factor of Staphylococcus aureus by core RNA polymerase
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Mondal Rajkrishna
Ganguly Tridib
Chanda Palas Kumar
Bandhu Amitava
Jana Biswanath
Sau Keya
Lee Chia Yen
Sau Subrata
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Abstract
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The primary sigma factor (σA) of Staphylococcus aureus, a potential drug target, was little investigated at the structural level. Using an N-terminal histidine-tagged σA (His-σA), here we have demonstrated that it exits as a monomer in solution, possesses multiple domains, harbors primarily α-helix and efficiently binds to a S. aureus promoter DNA in the presence of core RNA polymerase. While both N- and C-terminal ends of His- σA are flexible in nature, two Trp residues in its DNA binding region are buried. Upon increasing the incubation temperature from 25º to 40ºC, ~60% of the input His-σA was cleaved by thermolysin. Aggregation of His-σA was also initiated rapidly at 45oC. From the equilibrium unfolding experiment, the Gibbs free energy of stabilization of His-σA was estimated to be +0.70 kcal mol-1. The data together suggest that primary sigma factor of S. aureus is an unstable protein. Core RNA polymerase however stabilized σA appreciably.
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KEYWORD
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Primary sigma factor, Stability, Staphylococcus aureus, Structure
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