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Introduction

Neurotensin receptor 1 (NTSR1) is a G-protein coupled receptor (GPCR) that binds to the 13 amino acid peptide, neurotensin. Studies determining the structure of NTSR1 crystallized the GPCR bound with the C-terminus of its tridecapeptide ligand, because it has a higher potency and efficacy than its full-length counterpart. NTSR1 is a class A GPCR, and like all G-proteins, consists of an extracellular binding domain along with 7 transmembrane helices. Along with the ligand binding pocket at the top of the protein, NTSR1 also contains an allosteric Na+ ion binding pocket underneath. NTS binds to NTSR1, leading to a conformational change of the protein and modulation of second messengers. NTS has been shown to have a variety of biological activities including a role in the leptin signalling pathways, tumor growth, and dopamine regulation. The majority of effects of NTS are mediated through NTSR1. Research of the structure of NTSR1 has focused on the differences between its active and active-like states.

Pymol Pictures

Na+ Binding Pocket

, which is positioned at the bottom of the hydrophobic pocket(green link from allie), sets the top of the . The Na+ ion binding pocket acts as a negative allosteric site for G protein activity. When Na+ enters the Na+ ion binding pocket, it coordinates with Asp95, Gln131, and S135, and shuts down the activity of the protein. When the G protein is in its active state, the Na+ ion binding pocket is collapsed, preventing the regulation of protein activity through a Na+ ion. In this case, the Na+ ion is coordinated by a salt bridge to Asp113. The side chain atoms of Asp113 form a hydrogen bond network with Thr156, Ser361, Ser362, and Gln365, which prevents the coordination of a Na+ ion.

Neurotensin (Ligand)

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Function

Disease

Relevance

Structural highlights

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