Linked Life Data

9521753

Source:http://linkedlifedata.com/resource/pubmed/id/9521753

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
13
pubmed:dateCreated
1998-4-23
pubmed:abstractText
Four variants of human beta globin in which the Trp at position 37 has been replaced with a Tyr, Ala, Gly, or Glu have been expressed in Escherichia coli. These globins have been combined with normal human alpha chains and heme to form tetrameric hemoglobin molecules. A technique for the preparation of alpha chain dimers, which are cross-linked between their alpha99 lysine residues, has been developed, and these alpha dimers were combined with two of the beta globins, betaW37G and betaW37E, to form the corresponding cross-linked variants. The kinetics of CO binding to the deoxygenated derivatives following rapid mixing and of CO rebinding following flash photolysis have been examined as functions of pH in the presence and absence of the organic phosphate inositol hexaphosphate, IHP. The kinetic measurements indicate that replacement of the tryptophan with other residues destabilizes the hemoglobin tetramer, resulting in considerable dissociation of even the deoxygenated hemoglobins into alphabeta dimers at micromolar protein concentrations. Substitutions at beta37 also alter the properties of the deoxygenated hemoglobin tetramer. The alteration of the functional properties of the T states of these variants as well as the tendency of the deoxygenated derivatives to dissociate into alphabeta dimers increases in the order HbA < betaW37Y < betaW37A < betaW37G < betaW37E. Stabilizing the betaW37G or betaW37E tetramers by addition of IHP or by cross-linking does not restore the normal functional properties of the T state. Measurements of the geminate rebinding of CO establish a kinetic difference between the normal R state tetramer and the alphabeta dimer consistent with quaternary enhancement, the greater affinity of oxygen for the R state tetramer than for the alphabeta dimer. Kinetics of geminate rebinding also suggest that quaternary enhancement may be altered by substitutions at the beta37 position.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
31
pubmed:volume
37
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4325-35
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Preparation and kinetic characterization of a series of betaW37 variants of human hemoglobin A: evidence for high-affinity T quaternary structures.
pubmed:affiliation
Department of Medicine, University at Buffalo Veterans Administration Medical Center, Buffalo, New York 14215, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.