The role of hydration on the mechanism of allosteric regulation: In situ measurements of the oxygen-linked kinetics of water binding to hemoglobin

We report here the first direct measurements of changes in protein hydration triggered by a functional binding. This task is achieved by weighing hemoglobin (Hb) and myoglobin films exposed to an atmosphere of 98% relative humidity during oxygenation. The binding of the first oxygen molecules to Hb...

Descripción completa

Guardado en:
Detalles Bibliográficos
Autores principales: Salvay, Andrés Gerardo, Grigera, José Raúl, Colombo, Marcio F.
Formato: Articulo
Lenguaje:Inglés
Publicado: 2003
Materias:
Ciencias Exactas
protein hydration
Hemoglobin
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/84881
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-84881
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Exactas
protein hydration
Hemoglobin
spellingShingle Ciencias Exactas
protein hydration
Hemoglobin
Salvay, Andrés Gerardo
Grigera, José Raúl
Colombo, Marcio F.
The role of hydration on the mechanism of allosteric regulation: In situ measurements of the oxygen-linked kinetics of water binding to hemoglobin
topic_facet Ciencias Exactas
protein hydration
Hemoglobin
description We report here the first direct measurements of changes in protein hydration triggered by a functional binding. This task is achieved by weighing hemoglobin (Hb) and myoglobin films exposed to an atmosphere of 98% relative humidity during oxygenation. The binding of the first oxygen molecules to Hb tetramer triggers a change in protein conformation, which increases binding affinity to the remaining empty sites giving rise to the appearance of cooperative phenomena. Although crystallographic data have evidenced that this structural change increases the protein water-accessible surface area, isobaric osmotic stress experiments in aqueous cosolutions have shown that water binding is linked to Hb oxygenation. Now we show that the differential hydration between fully oxygenated and fully deoxygenated states of these proteins, determined by weighing protein films with a quartz crystal microbalance, agree with the ones determined by osmotic stress in aqueous cosolutions, from the linkage between protein oxygen affinity and water activity. The agreements prove that the changes in water activity brought about by adding osmolytes to the buffer solution shift biochemical equilibrium in proportion to the number of water molecules associated with the reaction. The concomitant kinetics of oxygen and of water binding to Hb have been also determined. The data show that the binding of water molecules to the extra protein surface exposed on the transition from the low-affinity T to the high-affinity R conformations of hemoglobin is the rate-limiting step of Hb cooperative reaction. This evidences that water binding is a crucial step on the allosteric mechanism regulating cooperative interactions, and suggests the possibility that environmental water activity might be engaged in the kinetic control of some important reactions in vivo.
format Articulo
Articulo
author Salvay, Andrés Gerardo
Grigera, José Raúl
Colombo, Marcio F.
author_facet Salvay, Andrés Gerardo
Grigera, José Raúl
Colombo, Marcio F.
author_sort Salvay, Andrés Gerardo
title The role of hydration on the mechanism of allosteric regulation: In situ measurements of the oxygen-linked kinetics of water binding to hemoglobin
title_short The role of hydration on the mechanism of allosteric regulation: In situ measurements of the oxygen-linked kinetics of water binding to hemoglobin
title_full The role of hydration on the mechanism of allosteric regulation: In situ measurements of the oxygen-linked kinetics of water binding to hemoglobin
title_fullStr The role of hydration on the mechanism of allosteric regulation: In situ measurements of the oxygen-linked kinetics of water binding to hemoglobin
title_full_unstemmed The role of hydration on the mechanism of allosteric regulation: In situ measurements of the oxygen-linked kinetics of water binding to hemoglobin
title_sort role of hydration on the mechanism of allosteric regulation: in situ measurements of the oxygen-linked kinetics of water binding to hemoglobin
publishDate 2003
url http://sedici.unlp.edu.ar/handle/10915/84881
work_keys_str_mv AT salvayandresgerardo theroleofhydrationonthemechanismofallostericregulationinsitumeasurementsoftheoxygenlinkedkineticsofwaterbindingtohemoglobin
AT grigerajoseraul theroleofhydrationonthemechanismofallostericregulationinsitumeasurementsoftheoxygenlinkedkineticsofwaterbindingtohemoglobin
AT colombomarciof theroleofhydrationonthemechanismofallostericregulationinsitumeasurementsoftheoxygenlinkedkineticsofwaterbindingtohemoglobin
AT salvayandresgerardo roleofhydrationonthemechanismofallostericregulationinsitumeasurementsoftheoxygenlinkedkineticsofwaterbindingtohemoglobin
AT grigerajoseraul roleofhydrationonthemechanismofallostericregulationinsitumeasurementsoftheoxygenlinkedkineticsofwaterbindingtohemoglobin
AT colombomarciof roleofhydrationonthemechanismofallostericregulationinsitumeasurementsoftheoxygenlinkedkineticsofwaterbindingtohemoglobin
bdutipo_str Repositorios
_version_ 1764820488673034242

Ejemplares similares