(67) THE MATRIX LOOPS PARTICIPATE IN CONTROL OF TRANSPORT IN THE UNCOUPLING PROTEIN UCP1

Eduardo Rial (1), M. Mar Gonzalez-Barroso (1), Christophe Fleury (2), M. Angeles Jimenez (3), Antonio Romero (1) and Frederic Bouillaud (2)
(1) Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
(2) CEREMOD, CNRS, Meudon, France
(3) Instituto Química-Física Rocasolano, CSIC, Madrid, Spain

The brown fat uncoupling protein UCP1 is a member of the mitochondrial carrier family that transports H+(OH-) and a variety of anions. UCP1 transport is regulated by fatty acids and nucleotides. We have previously described the homology between the region 261-269 of the UCP1 and the DNA binding domain of the estrogen receptor [1]. The deletion of amino acids 267-269 leads to the loss of the nucleotide regulation [2] while the elimination of the 9 amino acids converts the carrier into a pore [3]. We present the NMR structure of a 20 amino acids synthetic peptide that includes the 261-269 region and demonstrate the presence of alfa-helical structure in this UCP1 domain. Data obtained by NMR has been modelled to be linked to the 6th transmembrane helix by a beta turn. The resulting structure presents some interesting features that will be discussed. Site-directed mutagenesis reveals that the orientation of this domain may be critical for the regulation of transport in UCP1. Furthermore, the tripartite structure of the carrier family has allowed the performance of equivalent mutations in the first and second matrix loops of the UCP1 and similar effects are observed. We postulate that the three matrix loops constitute the gating domain of the UCP1.

[1] Bouillaud F, Casteilla L, Ricquier D. (1992). Mol. Biol. Evol. 9:970-975.
[2] Bouillaud F, Arechaga I, Petit PX, Raimbault S, Levi-Meyrueis C, Casteilla L, Laurent M, Rial E, Ricquier D (1994) EMBO J. 13:1990-1997.
[3] González-Barroso MM, Fleury C, Levi-Meyrueis C, Zaragoza P, Bouillaud F, Rial E (1997) Biochemistry 36:10930-10935.