Structural and functional study of a conserved region in the oncoupling protein UCP1: The three matrix loops are involved in the control of transport

Citation
Mm. Gonzalez-barroso et al., Structural and functional study of a conserved region in the oncoupling protein UCP1: The three matrix loops are involved in the control of transport, J MOL BIOL, 292(1), 1999, pp. 137-149
Citations number
64
Categorie Soggetti
Molecular Biology & Genetics
Journal title
JOURNAL OF MOLECULAR BIOLOGY
ISSN journal
00222836 → ACNP
Volume
292
Issue
1
Year of publication
1999
Pages
137 - 149
Database
ISI
SICI code
0022-2836(19990910)292:1<137:SAFSOA>2.0.ZU;2-P
Abstract
It has been reported that the region 261-269 of the uncoupling protein from brown adipose tissue mitochondria, UCP1, has an important role in the cont rol of its proton translocating activity. Thus the deletion of residues Phe 267-Lys268-Gly269 leads to the loss of the nucleotide regulation of the pro tein, while the complete deletion of the segment leads to the formation of a pore. The region displays sequence homology with the DNA-binding domain o f the estrogen receptor. The present report analyzes the structure, by NMR and circular dichroism, of a 20 amino acid residue peptide containing the r esidues of interest. We demonstrate that residues 263-268 adopt an a-helica l structure. The helix is at the N-terminal end of the sixth transmembrane domain. The functional significance of this helix has been examined by site -directed mutagenesis of the protein expressed recombinantly in yeasts. Alt erations in the structure or orientation of the region leads to an impairme nt of the regulation, by nucleotides and fatty acids, of the transport acti vity. UCP1 is one member of the family formed by the carriers of the mitoch ondrial inner membrane. The family is characterized by a tripartite structu re with three repeated segments of about 100 amino acid residues. Two of th e mutations have also been performed in the first and second matrix loops a nd the effect on UCP1: function is very similar. We conclude that the three matrix loops contribute to the formation of the gating domain in UCP1 and propose that they form a hydrophobic pocket that accommodates the purine mo iety of the bound nucleotide. (C) 1999 Academic Press.