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The Intrinsic Factor-Vitamin B12 Receptor, Cubilin, Is Assembled into Trimers via a Coiled-coil α-Helix

Lindblom, A., Quadt, N., Marsh, T., Aeschlimann, Daniel, Mörgelin, M., Mann, K., Maurer, P. and Paulsson, M. 1999. The Intrinsic Factor-Vitamin B12 Receptor, Cubilin, Is Assembled into Trimers via a Coiled-coil α-Helix. Journal of Biological Chemistry 274 (10) , pp. 6374-6380.

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Abstract

A large protein was purified from bovine kidney, using selective extraction with EDTA to solubilize proteins anchored by divalent cation-dependent interactions. An antiserum raised against the purified protein labeled the apical cell surface of the epithelial cells in proximal tubules and the luminal surface of small intestine. Ten peptide sequences, derived from the protein, all matched the recently published sequences for rat (Moestrup, S. K., Kozyraki, R., Kristiansen, M., Kaysen, J. H., Holm Rasmussen, H., Brault, D., Pontillon, F., Goda, F. O., Christensen, E. I., Hammond, T. G., and Verroust, P. J. (1998) J. Biol. Chem. 273, 5235-5242) and human cubilin, a receptor for intrinsic factor-vitamin B12 complexes, identifying the protein as bovine cubilin. In electron microscopy, a three-armed structure was seen, indicating an oligomerization of three identical subunits. This model was supported by the Mr values of about 1,500,000 for the intact protein and 440,000 for its subunits obtained by analytical ultracentrifugation. In a search for a potential assembly domain, we identified a region of heptad repeats in the N-terminal part of the cubilin sequence. Computer-assisted analysis supported the presence of a coiled-coil alpha-helix between amino acids 103 and 132 of the human cubilin sequence and predicted the formation of a triple coiled-coil. We therefore conclude that cubilin forms a noncovalent trimer of identical subunits connected by an N-terminal coiled-coil alpha-helix.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Dentistry
Subjects: Q Science > Q Science (General)
Publisher: American Society for Biochemistry and Molecular Biology
ISSN: 0021-9258
Last Modified: 04 Jun 2017 03:38
URI: http://orca.cf.ac.uk/id/eprint/23896

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