Linked Life Data

17253771

Source:http://linkedlifedata.com/resource/pubmed/id/17253771

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
7
pubmed:dateCreated
2007-2-13
pubmed:abstractText
The properties of three HbA variants with different mutations at the beta102 position, betaN102Q, betaN102T, and betaN102A, have been examined. All three are inhibited in their ligand-linked transition from the low affinity T quaternary state to the high affinity Re quaternary state. In the presence of inositol hexaphosphate, IHP, none of them exhibits cooperativity in the binding of oxygen. This is consistent with the destabilization of the Re state as a result of the disruption of the hydrogen bond that normally forms between the beta102 asparagine residue and the alpha94 aspartate residue in the Re state. However, these three substitutions also alter the properties of the T state of the hemoglobin tetramer. In the presence of IHP, the first two substitutions result in large increases in the ligand affinities of the beta-subunits within the T state structure. The betaN102A variant, however, greatly reduces the pH dependencies of the affinities of the alpha and beta subunits, K1(alpha) and K1(beta), respectively, for the binding of the first oxygen molecule in the absence of IHP. In the presence of IHP, the T state of this variant is strikingly similar to that of HbA under the same conditions. For both hemoglobins, K1(alpha) and K1(beta) exhibit only small Bohr effects. In the absence of IHP, the affinities of the alpha and beta subunits of HbA for the first oxygen are increased, and both exhibit greatly increased Bohr effects. However, in contrast to the behavior of HbA, the ligand-binding properties of the T state tetramer of the betaN102A variant are little affected by the addition or removal of IHP. It appears that along with its effect on the stability of the liganded Re state, this mutation has an effect on the T state that mimics the effect of adding IHP to HbA. It inhibits the set of conformational changes, which are coupled to the K1 Bohr effects and normally accompany the binding of the first ligand to the HbA tetramer in the absence of organic phosphates.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
20
pubmed:volume
46
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2037-49
pubmed:dateRevised
2007-12-3
pubmed:meshHeading
pubmed:year
2007
pubmed:articleTitle
Mutations of the betaN102 residue of HbA not only inhibit the ligand-linked T to Re state transition, but also profoundly affect the properties of the T state itself.
pubmed:affiliation
Department of Medicine, University at Buffalo, VA Western New York Healthcare System, Building 20, 3495 Bailey Avenue, Buffalo, New York 14215, USA.
pubmed:publicationType
Journal Article, Research Support, N.I.H., Extramural