1qab
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(New page: 200px<br /><applet load="1qab" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qab, resolution 3.20Å" /> '''The structure of hum...)
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Revision as of 22:24, 20 November 2007
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The structure of human retinol binding protein with its carrier protein transthyretin reveals interaction with the carboxy terminus of RBP
Overview
Whether ultimately utilized as retinoic acid, retinal, or retinol, vitamin, A is transported to the target cells as all-trans-retinol bound to, retinol-binding protein (RBP). Circulating in the plasma, RBP itself is, bound to transthyretin (TTR, previously referred to as thyroxine-binding, prealbumin). In vitro one tetramer of TTR can bind two molecules of, retinol-binding protein. However, the concentration of RBP in the plasma, is limiting, and the complex isolated from serum is composed of TTR and, RBP in a 1 to 1 stoichiometry. We report here the crystallographic, structure at 3.2 A of the protein-protein complex of human RBP and TTR., RBP binds at a 2-fold axis of symmetry in the TTR tetramer, and, consequently the recognition site itself has 2-fold symmetry: Four TTR, amino acids (Arg-21, Val-20, Leu-82, and Ile-84) are contributed by two, monomers. Amino acids Trp-67, Phe-96, and Leu-63 and -97 from RBP are, flanked by the symmetry-related side chains from TTR. In addition, the, structure reveals an interaction of the carboxy terminus of RBP at the, protein-protein recognition interface. This interaction, which involves, Leu-182 and Leu-183 of RBP, is consistent with the observation that, naturally occurring truncated forms of the protein are more readily, cleared from plasma than full-length RBP. Complex formation prevents, extensive loss of RBP through glomerular filtration, and the loss of, Leu-182 and Leu-183 would result in a decreased affinity of RBP for TTR.
About this Structure
1QAB is a Protein complex structure of sequences from Homo sapiens with RTL as ligand. Full crystallographic information is available from OCA.
Reference
The structure of human retinol-binding protein (RBP) with its carrier protein transthyretin reveals an interaction with the carboxy terminus of RBP., Naylor HM, Newcomer ME, Biochemistry. 1999 Mar 2;38(9):2647-53. PMID:10052934
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