Interaction of disulfides with methylcobaloxime

Brown, Kenneth L.; Jinkerson, David L.

doi:10.1016/s0022-328x(00)86705-4

Cited by 8 publications

(15 citation statements)

References 10 publications

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“…Brown and Jinkerson previously reported the prompt appearance of a charge transfer band at 322 nm upon exposure of Co(dmgH)2(CH3)(H2O) to 2-hydroxylethyl disulfide under alkaline aqueous conditions. 42 Together with our intact MS data, these findings suggested direct Cys ligation to the installed Co complex.…”

Section: Resultssupporting

confidence: 69%

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Engineering a Conformationally Switchable Artificial Metalloprotein

Fatima

Boggs

Thompson

et al. 2022

Preprint

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Most naturally occurring metalloenzymes are gated by rate-limiting conformational changes and there exists a critical inter-play between macroscopic structural rearrangements of the protein, and subatomic changes affecting the electronic struc-ture of embedded metallocofactors. Despite this connection, most artificial metalloproteins (ArMs) are prepared in structur-ally rigid protein hosts. To better model the natural mechanisms of metalloprotein reactivity, we have developed conforma-tionally switchable ArMs (swArMs) that undergo a large-scale structural rearrangement upon allosteric effector binding. The swArMs reported here contain a Co(dmgH)2(X) cofactor (dmgH = dimethylglyoxime, X = N3–, H3C–, iPr–). We used UV-vis absorbance and energy-dispersive X-ray fluorescence spectroscopies, along with protein assays, and mass spectrometry to show that these metallocofactors are installed site-specifically and stoichiometrically via direct Co‒S cysteine ligation within the E. coli glutamine binding protein (GlnBP). Structural characterization by single-crystal X-ray diffraction (2.99 Å resolu-tion) unveils the precise positioning and microenvironment of the metallocofactor within the protein fold. Fluorescence and circular dichroism spectroscopies, along with isothermal titration calorimetry reveal that allosteric Gln binding drives a large-scale protein conformational change. In swArMs containing a Co(dmgH)2(CH3) cofactor, we show that the protein stabilizes the otherwise labile Co‒S bond relative to the free complex. Kinetics studies performed as a function of temperature and pH reveal that the protein conformational change accelerates this bond dissociation in a pH-dependent fashion. We present swArMs as a robust platform for investigating the interplay between allostery and metallocofactor regulation.

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Section: Resultssupporting

confidence: 69%

“…We observe this ligand exchange by both 1 H-NMR and UV-vis absorption spectroscopies. 42,45 UV-vis absorbance changes reveal the disappearance of the peak at 325 nm and appearance of peaks at 380 nm and 440 nm that closely match the changes observed upon addition of Gln to apo-[Co(CH3)]-GlnBP (Figure S14).…”

Section: Resultssupporting

confidence: 61%

Engineering a Conformationally Switchable Artificial Metalloprotein

Fatima

Boggs

Thompson

et al. 2022

Preprint

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“…Formation of the organocobaloxime thiolato complex [CH 3 SCo(DH) 2 CH 3 ] - in 1:1 CD 3 OD:D 2 O solution was suggested 14 on the basis of the upfield shift of the 1 H NMR signal for CH 3 S - relative to the signal for free CH 3 S - . Loss of CH 3 SH under reduced pressure from the isolated compound [AsPh 4 ][CH 3 SCo(DH) 2 CH 3 ] prevented its characterization by elemental analysis . We successfully prepared [AsPh 4 ][EtSCo(DH) 2 CH 3 ] by reaction of H 2 OCo(DH) 2 CH 3 with NaSEt (reaction iii), and we were able to characterize the compound by elemental analysis and X-ray crystallography (see above).…”

Section: Resultsmentioning

confidence: 99%

“…The thiolate ligation reaction pathway (reaction iii) has been invoked in several instances for MeCbl and organocobalt B 12 models, although no characterized isolated complexes of this type have been reported. The first reports of thiolato organocobaloximes 9 and imine/oxime-type organocobalt(III) complexes {[LCo((DO)(DOH)pn)R]X, Chart } used UV−vis measurements as evidence of thiolate ligation. , Later, 1 H NMR evidence for a thiolato organocobaloxime was presented, but the isolated complex could not be adequately characterized however, this complex was not isolated.…”

Section: Introductionmentioning

confidence: 99%

“…The mechanisms of several reactions involving Co species and sulfur compounds are not fully understood, but these could involve Co species with coordinated sulfur ligands. For example, H 2 OCo(DH) 2 CH 3 was used as a catalyst to cleave disulfides in basic solution . In another system, CoCl 2 in the presence of organohalides appeared to mimic MeCbl-dependent enzymes and produced thioethers from thiols …”

Section: Introductionmentioning

confidence: 99%

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The First X-ray Structural Evidence Demonstrating Thiolate Coordination in an Organocobalt B₁₂Model Complex: Implications for Methionine Synthase

1997

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Enzyme-bound methyl-B 12 transfers its methyl group to homocysteine during methionine synthesis. However, treatment of several types of organocobalt B 12 models with arene-and alkanethiolates under ambient conditions leads only to thiolate ligation. The structure of [AsPh 4 ][EtSCo(DH) 2 CH 3 ] (DH ) monoanion of dimethylglyoxime), the first characterization by X-ray crystallography of an organocobalt complex containing a unidentate coordinated thiolate, demonstrates unambiguously the S-ligation of ethanethiolate to Co, trans to the CH 3 ligand. This compound contains a very long Co-S bond (2.342(2) Å). However, the length of the Co-C bond (2.005(7) Å) is typical; this result strongly supports reported FT-Raman spectroscopic data indicating that the thiolate-type ligand does not have a strong trans influence and does not significantly weaken the Co-C bond in the ground state. Since a strong trans influence alkyl ligand weakens the trans Co-C bond, we examined the effect of EtSon Co-((DO)(DOH)pn)(CH 3 ) 2 [(DO)(DOH)pn ) N 2 ,N 2′ -propanediylbis(2,3-butanedione 2-imine 3-oxime) is an imine/ oxime quadridentate ligand]. Even for this compound, no attack on the Co-C bond was observed, although independently synthesized EtSCo((DO)(DOH)pn)CH 3 was stable. Furthermore, thiolate did not cleave the Co-C bond of an organocobalt complex with a highly distorted Co-C group. Several new spectroscopic and ligandexchange reactions were observed in this study. Ligand-responsive NMR shift trends in these other new complexes also indicate that thiolate ligands have a weak trans influence.

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