title: Mercury(II) binding to s4U in E. coli tRNA(Val).
abstract: The accessibility of the s(4)U base in native tRNA(Val) from E.coli was monitored by studying the binding of various mercurials. The relative binding order HgBr(2)[unk]HgCl(2)>>CH(3)HgOAc[unk]CH(3)HgCl[unk]PCMB parallels approximately the steric requirements of linear HgX(2) or RHgX compounds for S(N)2 displacement by sulfur, although other factors are operative. Para-chloromercuri-benzoate (PCMB) does not bind the thiolated nucleotide unless the tertiary structure of the tRNA is opened up by removal of Mg(2+) ions and heating to 40 degrees . Under these conditions, equilibrium dialysis measurements using (14)C-labeled PCMB showed one binding site (n = 0.93) with an association constant, K(1), of 9 x 10(4)M(-1).
authors.forename: H R
authors.initials: HR
authors.lastname: Sunshine
authors.forename: S J
authors.initials: SJ
authors.lastname: Lippard
mesh_terms: D001665:Binding Sites; D004926:Escherichia coli / Q000378:metabolism; D007700:Kinetics; D008628:Mercury / Q000378:metabolism*; D009941:Organomercury Compounds / Q000378:metabolism; D012366:RNA, Transfer, Val / Q000737:chemistry / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D020245:p-Chloromercuribenzoic Acid / Q000378:metabolism
chemical_list: D009941:Organomercury Compounds; D012366:RNA, Transfer, Val; D020245:p-Chloromercuribenzoic Acid; D008628:Mercury