Stabilization of the primary sigma factor of Staphylococcus aureus by core RNA polymerase.
The primary sigma factor (sigma(A)) of Staphylococcus aureus, a potential drug target, was little investigated at the structural level. Using an N-terminal histidine-tagged sigma(A) (His-sigma(A)), here we have demonstrated that it exits as a monomer in solution, possesses multiple domains, harbors primarily alpha-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- sigma(A) are flexible in nature, two Trp residues in its DNA binding region are buried. Upon increasing the incubation temperature from 25 degrees to 40 degrees C, 60% of the input His-sigma(A) was cleaved by thermolysin. Aggregation of His-sigma(A) was also initiated rapidly at 45( degrees )C. From the equilibrium unfolding experiment, the Gibbs free energy of stabilization of His-sigma(A) 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 sigma(A) appreciably.
Mondal
Rajkrishna
R
Department of Biochemistry, Bose Institute, Kolkata, India.
Ganguly
Tridib
T
Chanda
Palas K
PK
Bandhu
Amitava
A
Jana
Biswanath
B
Sau
Keya
K
Lee
Chia Y
CY
Sau
Subrata
S
D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D055550:Protein Stability; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000378:metabolism*
D011994:Recombinant Proteins; D012808:Sigma Factor; D012321:DNA-Directed RNA Polymerases