A novel 13 kDa cytoplasmic soluble protein is required for the nucleotide (MgATP) modulation of the Na/Ca exchange in squid nerve fibers.
FEBS Lett
; 401(1): 6-10, 1997 Jan 13.
Article
em En
| MEDLINE
| ID: mdl-9003795
The Na/Ca exchange is a highly regulated transport mechanism in which MgATP, a powerful modulatory intracellular substrate, has important implications for its function. As occurs with some preparations, in squid axons, nucleotide regulation is lost after membrane vesicle isolation. This has been a significant obstacle in the biochemical characterization of the MgATP effect. An important clue in solving this long-standing puzzle is presented in this work by showing that prolonged intracellular dialysis of squid axons produces a complete run down of the MgATP effect. Here we report that a soluble cytoplasmic factor isolated from fresh squid axoplasm and brain reconstitutes the MgATP stimulation of the Na-gradient-dependent 45Ca uptake in squid optic nerve membrane vesicles. Partial purification of this factor uncovers the presence of a novel 13 kDa soluble cytoplasmic protein (SCPr) which, when microinjected in ATP de-regulated dialyzed squid axons, completely restores the MgATP stimulation of Na(o)-dependent Ca efflux. We propose that in the squid preparation this SCPr constitutes the link between the nucleotide and target effector: the Na/Ca exchanger itself, or other plasma membrane structures which may secondarily interact with the exchanger.
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01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas
/
Proteínas de Transporte
/
Trifosfato de Adenosina
/
Citoplasma
/
Fibras Nervosas
Limite:
Animals
Idioma:
En
Revista:
FEBS Lett
Ano de publicação:
1997
Tipo de documento:
Article
País de afiliação:
Venezuela
País de publicação:
Reino Unido