title: Metal dependency for transcription factor rho activation.
abstract: The Escherichia coli rho transcription termination factor terminates select transcripts and rho activity requires Mg(2+). We investigated whether divalent metal ions other than Mg(2+) catalyze rho-dependent ATP hydrolysis to ADP and P(i) in vitro. The effects of 11 divalent metal ions (Be(2+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Hg(2+), Mn(2+), Ni(2+), Sr(2+), VO(2+), Zn(2+)) on ATPase activity were determined in the absence and presence of MgCl(2). Without MgCl(2), Ca(2+), Cd(2+), Co(2+), Cu(2+), Hg(2+), Mn(2+), Ni(2+), VO(2+), and Zn(2+) activated ATP hydrolysis with either hyberbolic (Ca(2+), Co(2+), Cu(2+), Hg(2+), VO(2+)), peak velocity (Cd(2+), Mn(2+), Zn(2+)), or sigmoidal (Ni(2+)) rate acceleration curves. Sr(2+) was found to be a nonactivator and Be(2+) an inhibitor of rho-dependent ATPase activity. The metals' effects were compared with Mg(2+) and gave different rank orders when either the velocity (V(max), V(peak)) or the efficiency (V(max)/K(M), V(peak)/K(M)) of ATP hydrolysis was used as the determinant (V: Mg(2+) approximately Mn(2+) > Zn(2+) > Co(2+) > Ni(2+) approximately Cd(2+) > Ca(2+) > Cu(2+) > Hg(2+) approximately VO(2+); V/K(M): Mg(2+) > Mn(2+) > Ca(2+) > Co(2+) > Zn(2+) > Cu(2+) > Ni(2+) > Hg(2+) > Cd(2+)). Mg(2+) proved to be the most effective divalent metal. We observed that the metal-dependent rates were affected by metal ion interactions with rho, RNA, and the buffer constituents. Significantly, replacement of the octahedral Mg(2+) ion by metals that typically prefer coordination spheres less than six (Cd(2+), Co(2+), Ni(2+), VO(2+), Zn(2+)) led to ATPase activity, suggesting that the putative Mg x ATP(2-) coordination sphere in rho does not need to remain fully intact for ATP hydrolysis.
authors.affiliation: Department of Chemistry, University of Houston, Houston Texas 77204-5641, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Weber
authors.forename: William R
authors.initials: WR
authors.lastname: Widger
authors.forename: Harold
authors.initials: H
authors.lastname: Kohn
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D025243:Bacterial Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry; D002104:Cadmium / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002413:Cations, Divalent / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D006868:Hydrolysis; D015636:Magnesium Chloride / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry*; D012234:Rho Factor / Q000737:chemistry / Q000378:metabolism*; D015032:Zinc / Q000737:chemistry
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D002413:Cations, Divalent; D029968:Escherichia coli Proteins; D019216:Metals, Heavy; D012234:Rho Factor; D002104:Cadmium; D015636:Magnesium Chloride; D003035:Cobalt; D008345:Manganese; D003300:Copper; D000255:Adenosine Triphosphate; D025243:Bacterial Proton-Translocating ATPases; C024504:bicozamycin; D015032:Zinc; D002118:Calcium