HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 283, Issue 20, 13627-13637, May 16, 2008

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 283/20/13627    most recent M800755200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Arias-Moreno, X. Articles by Ventura, S. PubMed PubMed Citation Articles by Arias-Moreno, X. Articles by Ventura, S. Social Bookmarking                      What's this?

Scrambled Isomers as Key Intermediates in the Oxidative Folding of Ligand Binding Module 5 of the Low Density Lipoprotein Receptor^*

Xabier Arias-Moreno¹², Joan L. Arolas¹³, Francesc X. Aviles, Javier Sancho⁴, and Salvador Ventura⁵

From the Institute for Biocomputation and Physics of Complex Systems and Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, E-50009 Zaragoza, Spain and Institut de Biotecnologia i Biomedicina and Department de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, E-08193 Bellaterra Spain

The ligand binding module five (LA5) of the low density lipoprotein receptor is a small, single-domain protein of 40 residues and three disulfide bonds with a calcium binding motif that is essential for its structure and function. Several mutations in LA5 have been reported to cause familial hypercholesterolemia by impairing a proper folding of the module. The current study reports the oxidative folding and reductive unfolding pathways of wild type and mutant LA5 modules through kinetic and structural analysis of the trapped intermediates. Wild type LA5 folding involves an initial phase of nonspecific packing where the sequential oxidation of its cysteines gives rise to complex equilibrated populations of intermediates. In the presence of calcium, the attainment of a coordination-competent conformation becomes the rate-limiting step of folding while binding of the ion funnels both thermodynamically and kinetically the folding reaction toward the native state. In the absence of calcium, a scrambled isomer (termed Xa) constitutes the global free energy minimum of the folding process. Xa and the native form are stable, inter-convertible species whose relative populations at equilibrium appear displaced in disease-linked mutants toward the scrambled form. Because stable scrambled isomers such as Xa avoid the exposition of reactive cysteines in misfolded modules, they might constitute a strategy to prevent wrong interactions with other domains during folding of the receptor. Comparison of the folding pathways of wild type and mutant LA5 provides the molecular basis to understand how LA modules fold into a functional conformation or upon mutation misfold and lead to disease.

Received for publication, January 29, 2008 , and in revised form, March 10, 2008.

^* This work was supported in part by Ministerio de Educación y Ciencia (MEC) Grants BIO2007-68046, BIO2004-05879, and BFU2007-61476/BMC, by PM076/2006 (Gobierno de Aragón, Spain), and by CeRBA and SGR00037 (Generalitat de Catalunya, Spain). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. S1–S6.

¹ Both authors contributed equally to this work and share first authorship.

² Recipient of a fellowship from the Basque government, Spain.

³ Beneficiary of the "Juan de la Cierva" Program of the MEC.Spain.

⁴ To whom correspondence may be addressed. Tel.: 34-976761286; Fax: 34-976762123; E-mail: jsancho{at}unizar.es. ⁵ To whom correspondence may be addressed. Tel.: 34-935868147; Fax: 34-935811264; E-mail: Salvador.Ventura{at}uab.es.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?