Binding affinity and capacity of putative adaptor-mediated sorting of a Type I membrane protein in Leishmania mexicana.
Mol Biochem Parasitol
; 142(2): 203-11, 2005 Aug.
Article
en En
| MEDLINE
| ID: mdl-15890416
ABSTRACT
The membrane-bound acid phosphatase (MBAP), a Type I membrane protein predominantly associated with endosomal/lysosomal structures of Leishmania mexicana promastigotes, contains motifs in its cytosolic COOH-terminal tail (-MEVWRRYMKFKNKQSEAIIV-COOH) akin to tyrosine- and di-leucine-based sorting signals in multicellular organisms. Here, we first show that the COOH-terminal residues IIV of MBAP, but not the Y-residue, are required for endosomal targeting, suggesting specific binding to an adaptor complex at the cell surface. We then determine whether specific binding can be saturated by analysing the efficiency of endosomal targeting for increasing numbers of MBAP molecules per cell. The ratio of the steady-state abundance of wild-type MBAP on the cell surface to MBAP on endosomes increases until the distribution is no longer different from that observed for a mutant MBAP which lacks the IIV-motif or for a glycosylphosphatidylinositol-anchored form, both of which are distributed according to bulk membrane flow. A quantitative analysis of these in vivo results indicates specific binding to a putative adaptor complex with an affinity of about 10-4M to 50,000 sorting sites on the cell surface.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Fosfatasa Ácida
/
Leishmania mexicana
/
Regulación de la Expresión Génica
/
Transporte de Proteínas
/
Proteínas Adaptadoras del Transporte Vesicular
/
Proteínas de la Membrana
Límite:
Animals
País/Región como asunto:
Mexico
Idioma:
En
Revista:
Mol Biochem Parasitol
Año:
2005
Tipo del documento:
Article
País de afiliación:
Alemania