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Elimination of a homologous domain of an intestinal hydrolase enhances trafficking and affects polarized sorting via altered membrane association
Author(s) -
Behrendt Marc,
Naim Hassan
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.811.4
Subject(s) - transport protein , chemistry , mutant , microbiology and biotechnology , homologous chromosome , membrane , brush border , hydrolase , golgi apparatus , lactase , biochemistry , biology , enzyme , endoplasmic reticulum , vesicle , gene
The transport‐competent precursor of human intestinal lactase‐phlorizin hydrolase, pro‐LPH, encompasses four homologous domains, whereby the domains III and IV represent the mature brush border enzyme (LPH[beta]). The influence of each of the homologous domains on the structural and functional characteristics of the pro‐LPH polypeptide has been analysed by directed restructuring of the domain composition. Removal of domain IV, which carries the lactase activity, results in accelerated transport kinetics and altered patterns of quaternary structure and membrane association. These novel biosynthetic features of the mutant ([Delta]IV) are directly associated with a retarded dimerization of this mutant in the Golgi and a reduced association with Tween 20‐resistant membranes in the ER. These non‐classical types of membrane microdomains have been shown to be implicated in an early sorting mechanism of membrane proteins. Another mutant that lacks domain III is partially folded and blocked in the ER. Domain III per se is transport competent, enzymatically active and efficiently sorted to the apical surface. Altogether, our data strongly suggest a regulatory role of the membrane associated domain IV in the trafficking of pro‐LPH, while domain III comprises all necessary information for apical sorting. This work has been supported by the German Research Council.