Stereochemical control over manganese(II)-thio versus manganese(II)-oxy coordination in adenosine 5'-O-(1-thiodiphosphate) complexes at the active site of creatine kinase

Abstract

The stereochemical configurations of the Mn(II) complexes with the resolved epimers of adenosine 5'-O-(1-thiodiphosphate) (ADP alpha S), bound at the active site of creatine kinase, have been determined in order to assess the relative strengths of enzymic stereoselectivity versus Lewis acid/base preferences in metal-ligand binding. Electron paramagnetic resonance (EPR) data have been obtained for Mn(II) in anion-stabilized, dead-end (transition-state analogue) complexes, in ternary enzyme-MnIIADP alpha S complexes, and in the central complexes of the equilibrium mixture. The modes of coordination of Mn(II) at P alpha in the nitrate-stabilized, dead-end complexes with each epimer of ADP alpha S were ascertained by EPR measurements with (Rp)-[alpha-17O]ADP alpha S and (Sp)-[alpha-17O]ADP alpha S. The EPR spectrum for the complex with (Rp)-[alpha-17O]ADP alpha S showed inhomogeneous broadening due to unresolved superhyperfine coupling from coordinated 17O at P alpha. By contrast, the EPR spectrum for Mn(II) in complex with (Sp)-[alpha-17O]ADP alpha S is indistinguishable from that obtained for a matched sample with unlabeled (Sp)-ADP alpha S. A reduction in the magnitude of the 55Mn hyperfine coupling constant in the spectrum for the complex containing (Sp)-ADP alpha S is indicative of Mn(II)-thio coordination at P alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Stereochemistry of metal ion coordination to the terminal thiophosphoryl group of adenosine 5'-O-(3-thiotriphosphate) at the active site of pyruvate kinase

“…terized, binding determinant. Of the two divalent cations, Mn2* would have the greater propensity to accommodate a thio ligand (Smithers et al, 1989), and the data of Figure 2 clearly show that Mn2+ coordinates to the pro-R oxygen. It is probable, therefore, that Mg2+ (at site II) coordinates to the pro-S oxygen in preference to the thio substituent.…”

The17O Hyperfine Interaction in V17O(H217O)52+and Mn(H217O)62+Determined by High Field ENDOR Aided by DFT Calculations

“…When the couplings are large they can be resolved in the EPR spectrum, but when they are on the order of a few gauss, they are often hard to resolve. X-band electron spin echo envelope modulation (ESEEM) has been rarely used to probe 17 O hyperfine couplings, 3 but recently Q-band HYSCORE (hyperfine sublevel correlation spectroscopy) has been shown to be useful in the determination of 17 O hyperfine couplings. 4 EPR and ENDOR of high spin metal ions is a challenge, especially at the conventional X-band frequencies.…”

“…4 EPR and ENDOR of high spin metal ions is a challenge, especially at the conventional X-band frequencies. For instance, Mn 2+ has an electronic spin S ) 5 / 2 and at 9 GHz the 17 O Zeeman interaction is small, hence even at low temperatures all the M S ) ( 5 / 2 , ( 3 / 2 , ( 1 / 2 states contribute to the ENDOR spectrum. In the case of Mn(H 2 O) 6 2+ some of the 17 O (ν I ≈ 2.02 MHz) signals overlap with the 1 H (ν I ≈ 14.90 MHz).…”

17O hyperfine and quadrupole interactions for water ligands in frozen solutions of high spin Mn2+

“…For example, in phosphate kinases Mn 2ϩ ͑like Mg 2ϩ ͒ enhances catalysis of phosphate transfer through charge stabilization, charge shielding, and substrate alignment. 3,4 The purpose of the present study is to provide a methodology for electron nuclear double resonance ͑ENDOR͒ and electron spin echo envelope modulation ͑ESEEM͒ experiments and interpretation on 17 O-water ligated to Mn 2ϩ in frozen solutions. ͓Mn͑H 2 17 O͒ 6 ͔ 2ϩ was chosen for this initial study because it is chemically a relatively simple system with only one chemical type of 17 …”