Linked Life Data

2555518

Source:http://linkedlifedata.com/resource/pubmed/id/2555518

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1990-1-3
pubmed:abstractText
Structural features of the heme and the heme cavity of the monomeric hemoglobin (Hb) from the platyhelminth Dicrocoelium dendriticum were investigated by optical and proton nuclear magnetic resonance spectroscopy. Using nuclear Overhauser effects (NOEs) from resonances assigned previously through isotope labeling, most hyperfine-shifted resonances could be attributed to individual heme and protein protons in the cyano-metHb complex. It was observed that the heme 2-vinyl group is held in the trans orientation by nearby residues, whereas the 4-vinyl group exhibits an equilibrium between cis and trans orientations. NOE experiments in 1H2O allowed the identification of exchangeable protons belonging to the proximal histidine residue (F8) and to a distal residue. Detailed analysis of the NOE patterns obtained from the distal labile proton to non-labile protons and among these latter protons leads to the conclusion that a tyrosine side-chain occupies the distal site E7. Optical spectra of the alkaline-metHb also lead to this view, in that they are not typical of a hydroxy-metHb complex but instead resemble that of a hemin-phenolate or human mutant (M-type) Hb with a tyrosine residue linked to the iron atom. Further evidence for a distal tyrosine residue stems from the occurrence of an unusually stable transient ferrous Hb-cyanide complex, formed upon reduction of cyano-metHb to deoxy-Hb with dithionite. We suggest that the stability of this intermediate is due to a slow re-orientation of a large distal side-chain prior to cyanide dissociation. The sequence of the E-helix, known from the partially determined primary structure, was realigned to accommodate these findings. A frame-shift by one residue now positions a tyrosine at the distal site E7 instead of the originally proposed glycine residue.
pubmed:grant
pubmed:commentsCorrections
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0022-2836
pubmed:author
pubmed:issnType
Print
pubmed:day
20
pubmed:volume
209
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
235-47
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1989
pubmed:articleTitle
Structural and electronic properties of the liver fluke heme cavity by nuclear magnetic resonance and optical spectroscopy. Evidence for a distal tyrosine residue in a normally functioning hemoglobin.
pubmed:affiliation
Department of Chemistry, University of California, Davis 95616.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't