Magnetic resonance studies of the manganese guanosine di- and triphosphate complexes with elongation factor Tu.

摘要: Abstract Analysis of titration data EF-Tu-GDP with Mn(II) where free and bound were determined by proton relaxation rate water (PRR) yields one tight binding site a value 2 muM for the dissociation constant from EF-Tu-MnGDP complex, K'A. The manganese nucleotide ternary K2, 0.2 muM, was derived known Ks, binary complex excess GDP as titrant. apparent number, n, rapidly exchanging ligands coordinated to in is estimated frequency dependence PRR be approximately 1. n values enhancements, epsilont = 4.3 at 21 degrees, 24.3 MHZ 4.1 GTP are unusually low protein-Mn-nucleotide complexes. antibiotic X5108 which induces GTPase activity EF-Tu-MgGTP shown bind stoichiometrically thereby change enhancement 7.4. characteristic broad lines EPR spectra nucleotides strikingly narrowed upon EF-Tu. long electron spin times inferred indicate limited access solvent first coordination sphere its EF-Tu-nucleotide indicates that time, T1e, dominant process modulating Mn(II)-H2O interaction consequently determines correlation time. experiments 2.5 ns consistent lower limit T1e obtained line widths spectrum complex. Upon stoichiometric quantity X5108, severely broadened indicating greater sphere, i.e. an opening already suggested increased enhancement.