Co(<scp>ii</scp>)/Co(<scp>i</scp>) reduction-induced axial histidine-flipping in myoglobin reconstituted with a cobalt tetradehydrocorrin as a methionine synthase model

Hayashi, Takashi; Morita, Yoshitsugu; Mizohata, Eiichi; Oohora, Koji; Ohbayashi, Jun; Inoue, Tsuyoshi; Hisaeda, Yoshio

doi:10.1039/c4cc05448b

Cited by 40 publications

(67 citation statements)

References 19 publications

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“…The UV-Vis absorption spectrum of rHRP(Co II (TDHC)) in 50 mM phosphate buffer at pH 7.0 in Fig. 2a and Table 1 has a sharp absorption band at 513 nm, which is similar to the absorption at 510 nm in rMb(Co II (TDHC)), indicating His ligation to the cobalt center [29]. CD spectral changes in the far-UV region occurring with addition of the cofactor indicate an increasing negative Cotton effect at 222 nm in Fig.…”

Section: Reconstitution Of Hrp With Co II (Tdhc)mentioning

confidence: 86%

“…Distilled water was demineralized using a Millipore Integral-3 apparatus. Synthesis of cobalt tetradehydrocorrin, Co(TDHC), was described in our previous report [29]. HRP was purchased from Sigma-Aldrich (Type VI, salt-free lyophilized powder: P8375) and used without further purification.…”

Section: Methodsmentioning

confidence: 99%

“…2b). The interaction of the cobalt nucleus (I = 7/2) with the unpaired electron in a pentacoordinate low-spin d 7 configuration of Co(II) results in hyperfine splitting of the signal into an octet centered at g z = 1.99, and the presence of a 14 N (I = 1) ligand attached to the axial position of the Co II (TDHC) complex shows superhyperfine splitting of each component of the octet into a triplet [29]. This provides support for our proposal that the cobalt atom coordinates to the Nε2-atom of the His170 imidazole ring as an axial ligand.…”

Section: Reconstitution Of Hrp With Co II (Tdhc)mentioning

confidence: 98%

“…is sufficient to complete the reconstitution. X-ray crystal structure analysis shows that the ratio of occupancy of the enantiomers rMb(Co II ((1R,19R)-TDHC)) and rMb(Co II ((1S,19S)-TDHC)) is 13:7 [29]. The abovementioned requirement for two equivalents of Co II (TDHC) cofactor may be an indication that apoHRP selectively binds one of the Co II (TDHC) enantiomers of Co II (TDHC) because the heme pocket of HRP accurately recognizes the position of the methyl groups in contrast to the heme pocket of Mb.…”

Section: Reconstitution Of Hrp With Co II (Tdhc)mentioning

confidence: 99%

“…Over the past decades, several model systems have been reported using cobalamin and its derivatives as well as cobalt corrinoid complexes [20][21][22][23][24][25][26][27][28]. Previously, our group reported the structure, reactivity and physicochemical properties of myoglobin (Mb) reconstituted with Co(TDHC), (TDHC = 8,12-dicarboxyethyl-1,2,3,7,13,17,18,19-octamethyltetradehydrocorrin), rMb(Co(TDHC)), in efforts to develop a useful proteinbased model of cobalamin-dependent methionine synthase [29][30][31][32]. Further replication of the coordination state of the native enzyme promises a more sophisticated model system.…”

Section: Introductionmentioning

confidence: 98%

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Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

et al. 2017

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Horseradish peroxidase was reconstituted with cobalt tetradehydrocorrin, rHRP(Co(TDHC)), as a structural analog of cobalamin coordinated with an imidazolate-like His residue, which is generally seen in native enzymes. In contrast to the previously reported cobalt tetradehydrocorrin-reconstituted myoglobin, rMb(Co(TDHC)), the HRP matrix was expected to provide strong axial ligation by His170 which has imidazolate character. rHRP(Co(TDHC)) was characterized by EPR and its reaction with reductants indicates a negative shift of its redox potential compared to rMb(Co(TDHC)). Furthermore, aqua- and CN-forms of Co(III) state were prepared. The former species was obtained by oxidation of rHRP(Co(TDHC)) with K[Fe(CN)]. The cyanide-coordinated Co(III) species in the latter was prepared by ligand exchange of rHRP(Co(OH)(TDHC)) with exogenous cyanide upon addition of KCN. The C NMR chemical shift of cyanide in rHRP(Co(CN)(TDHC)) was determined to be 121.8 ppm. IR measurements show that the cyanide of rHRP(Co(CN)(TDHC)) has a stretching frequency peak at 2144 cm. The C NMR and IR measurements indicate strong coordination of cyanide to Co(TDHC) relative to rMb(Co(CN)(TDHC)). Thus, the extent of π-back donation from the cobalt ion to the cyanide ion is relatively high in rHRP(Co(CN)(TDHC)). The pK values of rHRP(Co(OH)(TDHC)) and rHRP(Co(CN)(TDHC)) are the same (pK = 3.2) as determined by a pH titration experiment, indicating that cyanide ligation does not affect Co-His ligation, whereas cyanide ligation weakens the Co-His ligation in rMb(Co(CN)(TDHC)). Taken together, these results indicate that HRP reconstituted with cobalt tetradehydrocorrin is a suitable cobalamin-dependent enzyme model with imidazolate-like His residue.

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Section: Reconstitution Of Hrp With Co II (Tdhc)mentioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Section: Reconstitution Of Hrp With Co II (Tdhc)mentioning

confidence: 98%

Section: Reconstitution Of Hrp With Co II (Tdhc)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

et al. 2017

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Myoglobin Reconstituted with Ni Tetradehydrocorrin as a Methane‐Generating Model of Methyl‐coenzyme M Reductase

2019

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Myoglobin reconstituted with Ni tetradehydrocorrin was investigated as a model of F430‐containing methyl‐coenzyme M reductase, which catalyzes anaerobic methane generation. The NiII tetradehydrocorrin complex has a NiII/NiI redox potential of −0.34 V vs. SHE and EPR spectroscopy indicates the formation of a NiI species upon reduction by dithionite. This redox potential is approximately 0.31 V more positive than that of F430. The NiI tetradehydrocorrin moiety is bound to the apo‐form of myoglobin to yield the reconstituted protein. Methane gas is generated in the reaction of the model with methyl iodide in the presence of the reconstituted protein under reductive conditions, whereas the NiI complex itself does not produce methane gas. This is the first example of a protein‐based functional model of F430‐containing methyl‐coenzyme M reductase.

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Myoglobin Reconstituted with Ni Tetradehydrocorrin as a Methane‐Generating Model of Methyl‐coenzyme M Reductase

2019

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Myoglobin reconstituted with Ni tetradehydrocorrin was investigated as am odel of F430-containing methylcoenzyme Mr eductase,w hich catalyzesa naerobic methane generation. The Ni II tetradehydrocorrin complex has aNi II /Ni I redox potential of À0.34 Vv s. SHE and EPR spectroscopy indicates the formation of aN i I species upon reduction by dithionite.T his redox potential is approximately 0.31 Vm ore positive than that of F430. The Ni I tetradehydrocorrin moiety is bound to the apo-form of myoglobin to yield the reconstituted protein. Methane gas is generated in the reaction of the model with methyl iodide in the presence of the reconstituted protein under reductive conditions,whereas the Ni I complex itself does not produce methane gas.This is the first example of aproteinbased functional model of F430-containing methyl-coenzyme Mreductase.

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Co(ii)/Co(i) reduction-induced axial histidine-flipping in myoglobin reconstituted with a cobalt tetradehydrocorrin as a methionine synthase model

Cited by 40 publications

References 19 publications

Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

Myoglobin Reconstituted with Ni Tetradehydrocorrin as a Methane‐Generating Model of Methyl‐coenzyme M Reductase

Myoglobin Reconstituted with Ni Tetradehydrocorrin as a Methane‐Generating Model of Methyl‐coenzyme M Reductase

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