Publication Date:
2012-10-23
Description:
In human cells, cytosolic citrate is a chief precursor for the synthesis of fatty acids, triacylglycerols, cholesterol and low-density lipoprotein. Cytosolic citrate further regulates the energy balance of the cell by activating the fatty-acid-synthesis pathway while downregulating both the glycolysis and fatty-acid beta-oxidation pathways. The rate of fatty-acid synthesis in liver and adipose cells, the two main tissue types for such synthesis, correlates directly with the concentration of citrate in the cytosol, with the cytosolic citrate concentration partially depending on direct import across the plasma membrane through the Na(+)-dependent citrate transporter (NaCT). Mutations of the homologous fly gene (Indy; I'm not dead yet) result in reduced fat storage through calorie restriction. More recently, Nact (also known as Slc13a5)-knockout mice have been found to have increased hepatic mitochondrial biogenesis, higher lipid oxidation and energy expenditure, and reduced lipogenesis, which taken together protect the mice from obesity and insulin resistance. To understand the transport mechanism of NaCT and INDY proteins, here we report the 3.2 A crystal structure of a bacterial INDY homologue. One citrate molecule and one sodium ion are bound per protein, and their binding sites are defined by conserved amino acid motifs, forming the structural basis for understanding the specificity of the transporter. Comparison of the structures of the two symmetrical halves of the transporter suggests conformational changes that propel substrate translocation.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3617922/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3617922/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mancusso, Romina -- Gregorio, G Glenn -- Liu, Qun -- Wang, Da-Neng -- P30 EB009998/EB/NIBIB NIH HHS/ -- R01 DK053973/DK/NIDDK NIH HHS/ -- R01 GM093825/GM/NIGMS NIH HHS/ -- R01 MH083840/MH/NIMH NIH HHS/ -- R01-DK073973/DK/NIDDK NIH HHS/ -- R01-GM093825/GM/NIGMS NIH HHS/ -- R01-MH083840/MH/NIMH NIH HHS/ -- U54 GM075026/GM/NIGMS NIH HHS/ -- U54-GM075026/GM/NIGMS NIH HHS/ -- England -- Nature. 2012 Nov 22;491(7425):622-6. doi: 10.1038/nature11542. Epub 2012 Oct 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉The Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, New York 10016, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23086149" target="_blank"〉PubMed〈/a〉
Keywords:
Amino Acid Motifs
;
Amino Acid Sequence
;
Binding Sites
;
Citric Acid/chemistry/metabolism
;
Crystallography, X-Ray
;
Dicarboxylic Acid Transporters/*chemistry/*metabolism
;
Ion Transport
;
Models, Molecular
;
Molecular Sequence Data
;
Protein Conformation
;
Sodium/chemistry/metabolism
;
Structural Homology, Protein
;
Structure-Activity Relationship
;
Vibrio cholerae/*chemistry
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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