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Biochem Biophys Res Commun. 1999 Jun 24;260(1):188-92.

Substitution of the two carboxyl-terminal serines by alanine causes retention of MAL, a component of the apical sorting machinery, in the endoplasmic reticulum.

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Centro de Biología Molecular "Severo Ochoa,", Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, Madrid, 28049-, Spain.


MAL, a selective resident of glycolipid-enriched membranes (GEMs), is an integral membrane protein necessary for apical transport and accurate sorting of the influenza virus hemagglutinin in MDCK cells. The carboxyl-terminal end of MAL has the sequence Phe-Ser-Leu-Ile-Arg-Trp-Lys-Ser-Ser (FSLIRWKSS), which includes the LIRW motif necessary for sorting MAL to GEMs, and whose last five amino acids resemble dilysine-based signals involved in endoplasmic reticulum (ER) retention. We have addressed the influence of the carboxyl-terminal serines in both MAL distribution and incorporation into GEMs. Substitution of the serines by alanine impeded the access of MAL to GEMs and changed its distribution from a perinuclear distribution to an ER pattern. The RWKSS sequence appended to the carboxyl-terminus of CD4 caused retention of the chimera in the ER. Thus, although this pentapeptide can function producing ER retention in other protein context, the presence of the carboxyl-terminal serines in the intact MAL molecule prevents its use as an ER-retention signal.

[Indexed for MEDLINE]

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