[28] Vitamin B12

Allen, Robert H.; Burger, R. Michael; Mehlman, Carol S.; Majerus, Philip W.

doi:10.1016/s0076-6879(74)34031-1

Cited by 8 publications

(1 citation statement)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, cyanocobalamin can be formed from aquocobalamin when bound to chicken cobalophilin, while a dicyanide complex is not formed . The top axial ligand is also accessible to a solid support such as Sephacryl-(aminopropyl)cobalamin for affinity purification of the protein (Allen et al, 1974). The success of cobalamin affinity techniques in isolating cobalophilin confirms that the top axial ligand position could not be protected from oxygen diffusion by the protein.…”

Section: Discussionmentioning

confidence: 99%

Human cobalophilin: The structure of bound methylcobalamin and a functional role in protecting methylcobalamin from photolysis

Frisbie¹,

Chance²

1993

Biochemistry

View full text Add to dashboard Cite

The interactions of methylcobalamin with cobalophilin from human serum were analyzed using extended X-ray absorption fine structure (EXAFS) spectroscopy, photolysis of the cobalt-carbon bond of methylcobalamin, and a pKa determination of the protonation of the coordinated nitrogen of 5,6-dimethylbenzimidazole (DMB). These results are consistent with the idea that the DMB nitrogen is still coordinated when protein is bound; however, the ability of a methyl radical (generated by photolysis) to escape the geminate cage of the protein is considerably reduced. For methylcobalamin in solution, the DMB nitrogen ligand is at a distance of 2.20 +/- 0.03 A from cobalt [Sagi, I., & Chance, M. R. (1992) J. Am. Chem. Soc. 114, 8061-8066]. This distance to the lower axial ligand does not change when protein binds (2.20 +/- 0.04 A), nor do the optical spectra exhibit any base-off character. The average of the distance from cobalt to the four equatorial nitrogens of the corrin plane is also unchanged. The pKa for the conversion of the "base-on" to the "base-off" form of methylcobalamin, where the above DMB nitrogen becomes protonated and the Co-N axial bond is cleaved, does not deviate from the free cobalamin value of 2.7 when methylcobalamin is bound to cobalophilin. These results indicate that replacement of the DMB ligand with a ligand from the protein is unlikely. Although the background-subtracted EXAFS data sets for free methylcobalamin and for the protein complex are extremely similar, more accurate data with explicit higher shell analysis would be required to entirely rule out ligand replacement. The chemical and electronic nature of the ligand changes little.(ABSTRACT TRUNCATED AT 250 WORDS)

show abstract

Section: Discussionmentioning

confidence: 99%

Human cobalophilin: The structure of bound methylcobalamin and a functional role in protecting methylcobalamin from photolysis

Frisbie¹,

Chance²

1993

Biochemistry

View full text Add to dashboard Cite

show abstract

Purification of methylmalonyl-CoA mutase from Propionibacterium shermanii using affinity chromatography

Murthy

Jones

Cole

et al. 1977

Biochimica et Biophysica Acta (BBA) - Enzymology

View full text Add to dashboard Cite

Affinity chromatography of N⁵‐methyltetrahydropfolate‐homocysteine methyltransferase on a cobalamin‐sepharose

1978

View full text Add to dashboard Cite

[28] Vitamin B12

Cited by 8 publications

References 7 publications

Human cobalophilin: The structure of bound methylcobalamin and a functional role in protecting methylcobalamin from photolysis

Human cobalophilin: The structure of bound methylcobalamin and a functional role in protecting methylcobalamin from photolysis

Purification of methylmalonyl-CoA mutase from Propionibacterium shermanii using affinity chromatography

Affinity chromatography of N⁵‐methyltetrahydropfolate‐homocysteine methyltransferase on a cobalamin‐sepharose

Contact Info

Product

Resources

About

[28] Vitamin B12

Cited by 8 publications

References 7 publications

Human cobalophilin: The structure of bound methylcobalamin and a functional role in protecting methylcobalamin from photolysis

Human cobalophilin: The structure of bound methylcobalamin and a functional role in protecting methylcobalamin from photolysis

Purification of methylmalonyl-CoA mutase from Propionibacterium shermanii using affinity chromatography

Affinity chromatography of N5‐methyltetrahydropfolate‐homocysteine methyltransferase on a cobalamin‐sepharose

Contact Info

Product

Resources

About

Affinity chromatography of N⁵‐methyltetrahydropfolate‐homocysteine methyltransferase on a cobalamin‐sepharose