A cytosolic trans-activation domain essential for ammonium uptake.
Nature
; 446(7132): 195-8, 2007 Mar 08.
Article
em En
| MEDLINE
| ID: mdl-17293878
ABSTRACT
Polytopic membrane proteins are essential for cellular uptake and release of nutrients. To prevent toxic accumulation, rapid shut-off mechanisms are required. Here we show that the soluble cytosolic carboxy terminus of an oligomeric ammonium transporter from Arabidopsis thaliana serves as an allosteric regulator essential for function; mutations in the C-terminal domain, conserved between bacteria, fungi and plants, led to loss of transport activity. When co-expressed with intact transporters, mutants inactivated functional subunits, but left their stability unaffected. Co-expression of two inactive transporters, one with a defective pore, the other with an ablated C terminus, reconstituted activity. The crystal structure of an Archaeoglobus fulgidus ammonium transporter (AMT) suggests that the C terminus interacts physically with cytosolic loops of the neighbouring subunit. Phosphorylation of conserved sites in the C terminus are proposed as the cognate control mechanism. Conformational coupling between monomers provides a mechanism for tight regulation, for increasing the dynamic range of sensing and memorizing prior events, and may be a general mechanism for transporter regulation.
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Base de dados:
MEDLINE
Assunto principal:
Proteínas de Plantas
/
Ativação Transcricional
/
Arabidopsis
/
Proteínas de Transporte de Cátions
/
Citosol
/
Compostos de Amônio Quaternário
Idioma:
En
Ano de publicação:
2007
Tipo de documento:
Article