Inositol 1,4,5-Trisphosphate Receptor
From Proteopedia
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Inositol 1,4,5-trisphosphate receptor binding protein is a ubiquitous protein involved in the Ca2+ signalling processes in a variety of organisms [1]
Structure
The specific type of inositol 1,4,5-trisphosphate receptor (InsP3R)protein discussed here is the mouse type one InsP3R, also called InsP3R1. This polypeptide contains three major regions: the amino terminal inositol 1,4,5-trisphosphate (InsP3) binding region, the central modulatory region, and the carboxy-terminus channel region.1 The protein forms an L-shaped structure composed of two asymmetric domains perpendicular to each other.[1] The N-terminal domain is made up of 12 β-strands and 2 single-turn helices, which come together to form a barrel.[1] The C-terminal end is quite different, consisting of a bundle made of eight α-helices.[1] The interface of the two domains is lined with basic residues and forms the receptor site for InsP3.[1]
The protein fold of the β-domain can also be called the β-trefoil. This element is present in other proteins as well, including fibroblast growth factors and mannose receptors.[1] In the case of the InsP3R β-trefoil, the structure was found to be very similar to the β-trefoil of the mannose receptor. In the β-domain of InsP3R1, three of six two-stranded hairpins come together to form a barrel and the other three form a triangular cap for the barrel.[1]
The α-domain of InsP3R shows a high degree of homology with an element called an armidillo repeat fold found in proteins such as β-catenin and importins.[1] In β-catenin and importins, the armadillo repeat functions as a motif for protein-protein interactions.[1] Within the α-domain of mouse InsP3,
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Shannon King, Alexander Berchansky, Michal Harel, Ann Taylor, David Canner, Andrea Gorrell, Jaclyn Gordon
