Linked Life Data

21480614

Source:http://linkedlifedata.com/resource/pubmed/id/21480614

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
10
pubmed:dateCreated
2011-5-9
pubmed:abstractText
Human cystathionine ?-synthase (hCBS), a key enzyme in the trans-sulfuration pathway, catalyzes the condensation of serine with homocysteine to produce cystathionine. CBS from higher organisms is the only known protein that binds pyridoxal-5'-phosphate (PLP) and heme. Intriguingly, the function of the heme in hCBS has yet to be elucidated. Herein, we describe the characterization of a cobalt-substituted variant of hCBS (Co hCBS) in which CoPPIX replaces FePPIX (heme). Co(III) hCBS is a unique Co-substituted heme protein: the Co(III) ion is 6-coordinate, low-spin, diamagnetic, and bears a cysteine(thiolate) as one of its axial ligands. The peak positions and intensities of the electronic absorption and MCD spectra of Co(III) hCBS are distinct from those of previously Co-substituted heme proteins; TD-DFT calculations reveal that the unique features arise from the 6-coordinate Co bound axially by cysteine(thiolate) and a neutral donor, presumably histidine. Reactivity of Co(III) hCBS with HgCl(2) is consistent with a loss of the cysteine(thiolate) ligand. Co(III) hCBS is slowly reduced to Co(II) hCBS, which contains a 5-coordinate, low-spin, S = 1/2 Co-porphyrin that does not retain the cysteine(thiolate) ligand; this form of Co(II) hCBS binds NO((g)) but not CO((g)). Co(II) hCBS is reoxidized in the air to form a new Co(III) form, which does not contain a cysteine(thiolate) ligand. Canonical and alternative CBS assays suggest that maintaining the native heme ligation motif of wild-type Fe hCBS (Cys/His) is essential in maintaining maximal activity in Co hCBS. Correlation between the coordination structures and enzyme activity in both native Fe and Co-substituted proteins implicates a structural role for the heme in CBS.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
1520-510X
pubmed:author
pubmed:issnType
Electronic
pubmed:day
16
pubmed:volume
50
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4417-27
pubmed:meshHeading
pubmed-meshheading:21480614-Circular Dichroism, pubmed-meshheading:21480614-Cloning, Molecular, pubmed-meshheading:21480614-Cobalt, pubmed-meshheading:21480614-Coordination Complexes, pubmed-meshheading:21480614-Cystathionine beta-Synthase, pubmed-meshheading:21480614-Cysteine, pubmed-meshheading:21480614-Escherichia coli, pubmed-meshheading:21480614-Heme, pubmed-meshheading:21480614-Hemeproteins, pubmed-meshheading:21480614-Histidine, pubmed-meshheading:21480614-Humans, pubmed-meshheading:21480614-Hydrogen-Ion Concentration, pubmed-meshheading:21480614-Ligands, pubmed-meshheading:21480614-Models, Molecular, pubmed-meshheading:21480614-Oxidation-Reduction, pubmed-meshheading:21480614-Protein Binding, pubmed-meshheading:21480614-Protein Structure, Tertiary, pubmed-meshheading:21480614-Pyridoxal Phosphate, pubmed-meshheading:21480614-Recombinant Proteins, pubmed-meshheading:21480614-Spectrophotometry, Atomic
pubmed:year
2011
pubmed:articleTitle
Cobalt cystathionine ?-synthase: a cobalt-substituted heme protein with a unique thiolate ligation motif.
pubmed:affiliation
Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, Wisconsin 53706, USA.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural