Probing the nucleotide binding sites in T7 RNA polymerase using cibacron blue.
T7 RNA polymerase (T7 RNAP) is an enzyme that utilizes ribonucleotides to synthesize the nascent RNA chain in a template-dependent manner. In this work we have studied the interaction of T7 RNAP with cibacron blue, an anthraquinone monochlorotriazine dye, and its effect on the function of the enzyme. T7 RNAP binds to the dye in a bi-phasic manner. The first phase of the binding is characterized by a high affinity (Kd in the nanomolar range) and reversible inactivation of the enzyme. The second binding site is the common substrate binding site. The association of the dye with T7 RNAP is a good model to understand the physiological significance of a high affinity binding of the initiating nucleotide, GTP, earlier reported from our laboratory. The results will be discussed to understand the role of the high affinity GTP binding.
Das
M
M
Biophysics Division, Saha Institute of Nuclear Physics, 37, Belgachia Road, Calcutta 700 037, India.
Dasgupta
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D001665:Binding Sites; D001667:Binding, Competitive; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D014227:Triazines / Q000737:chemistry*; D014544:Uridine Triphosphate / Q000378:metabolism; D014764:Viral Proteins
D014227:Triazines; D014764:Viral Proteins; C012842:Cibacron Blue F 3GA; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases; D014544:Uridine Triphosphate