title: Absence of a phosphorylated intermediate during ATP hydrolysis by Escherichia coli transcription termination protein rho.
abstract: We have established the suitability of adenosine 5'-O-(gamma-thio)triphosphate(ATP gamma S) as an analog of ATP for the nucleoside triphosphatase activity of Escherichia coli transcription termination protein rho (EC 3.6.1.3). Steady-state analysis gives a Vmax of 1.5 mumol min-1 mg-1, 9% of the value with MgATP as substrate, and indicates that ATP gamma S binds as tightly (based on Km and Ki versus ATP) to rho as does ATP. (gamma-S)[beta gamma-17O,gamma-17O,gamma-18O]ATP gamma S was used as substrate to produce chiral product inorganic [17O,18O]thiophosphate and determine the stereochemical course of the hydrolysis. The results of this determination, inversion at the thiophosphoryl phosphorus, indicate that the enzymatic hydrolysis of ATP by rho consists of a direct transfer of the phospho group to water without the existence of a phosphoenzyme or phospho-RNA intermediate.
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008968:Molecular Conformation; D010766:Phosphorylation; D012234:Rho Factor / Q000494:pharmacology*; D014157:Transcription Factors / Q000494:pharmacology*
chemical_list: D012234:Rho Factor; D014157:Transcription Factors; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate