The role of amino acid alpha38 in the control of oxygen binding to human adult and embryonic haemoglobin Portland.
Biochem J
; 343 Pt 3: 681-5, 1999 Nov 01.
Article
em En
| MEDLINE
| ID: mdl-10527949
ABSTRACT
The role of the amino acid at position alpha(38) in haemoglobin has been probed using site-directed mutagenesis. When the Thr residue at position alpha(38) (which is totally conserved in all mammals) is changed to a Gln, the equilibrium properties of the protein are significantly altered. Equilibrium and kinetic data show that the R-state properties of the protein are essentially unaffected by the mutation whilst the allosteric equilibrium and T-state properties are changed. Mutation of the naturally occurring Gln(38) of the human embryonic haemoglobin zeta-chain (the only known non-Thr containing globin) to a Thr residue shows the converse change in properties produced by the adult mutation, although in this case the situation is complicated by significant chain heterogeneity in the T state. An extension of the two-state model of co-operativity is presented to describe quantitatively the equilibrium ligand binding in the presence of T-state chain heterogeneity. A molecular model is described in which the putative interaction of alphaGln(38) and betaTyr(145) is identified which make a significant contribution to the previously reported unusual ligand-binding properties of the zeta-chain containing human embryonic haemoglobins.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Oxigênio
/
Hemoglobina Fetal
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Hemoglobina A
/
Hemoglobinas Anormais
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Oxiemoglobinas
Idioma:
En
Ano de publicação:
1999
Tipo de documento:
Article