The solution structures of human Orexin-A

Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 30 
  • Selection Criteria: target function 

wwPDB Validation   3D Report Full Report

This is version 2.0 of the entry. See complete history


Orexin-A is composed of a highly conserved C-terminal and a specific, hydrophilic N-terminal region, revealing the structural basis of specific recognition by the orexin-1 receptor

Takai, T.Takaya, T.Nakano, M.Akutsu, H.Nakagawa, A.Aimoto, S.Nagai, K.Ikegami, T.

(2006) J Pept Sci 12: 443-454

  • DOI: https://doi.org/10.1002/psc.747
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Orexins-A and B, also called hypocretins-1 and 2, respectively, are neuropeptides that regulate feeding and sleep-wakefulness by binding to two orphan G protein-coupled receptors named orexin-1 (OX(1)R) and orexin-2 (OX(2)R). The sequences and functions of orexins-A and B are similar to each other, but the high sequence homology (68%) is limited in their C-terminal half regions (residues 15-33). The sequence of the N-terminal half region of orexin-A (residues 1-14), containing two disulfide bonds, is very different from that of orexin-B. The structure of orexin-A was determined using two-dimensional homonuclear and (15)N and (13)C natural abundance heteronuclear NMR experiments. Orexin-A had a compact conformation in the N-terminal half region, which contained a short helix (III:Cys6-Gln9) and was fixed by the two disulfide bonds, and a helix-turn-helix conformation (I:Leu16-Ala23 and II:Asn25-Thr32) in the remaining C-terminal half region. The C-terminal half region had both hydrophobic and hydrophilic residues, which existed on separate surfaces to provide an amphipathic character in helices I and II. The nine residues on the hydrophobic surface are also well conserved in orexin-B, and it was reported that the substitution of each of them with alanine resulted in a significant drop in the functional potency at the receptors. Therefore, we suggest that they form the surface responsible for the main hydrophobic interaction with the receptors. On the other hand, the residues on the hydrophilic surface, together with the hydrophilic residues in the N-terminal half region that form a cluster, are known to make only small contributions to the binding to the receptors through similar alanine-scan experiments. However, since our structure of orexin-A showed that large conformational and electrostatical differences between orexins-A and B were rather concentrated in the N-terminal half regions, we suggest that the region of orexin-A is important for the preference for orexin-A of OX(1)R.

  • Organizational Affiliation

    Institute for Protein Research, Osaka University, Yamadaoka 3-2, Osaka, 565-0871, Japan.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Orexin-A34Homo sapiensMutation(s): 0 
Membrane Entity: Yes 
UniProt & NIH Common Fund Data Resources
Find proteins for O43612 (Homo sapiens)
Explore O43612 
Go to UniProtKB:  O43612
GTEx:  ENSG00000161610 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO43612
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on PCA
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 30 
  • Selection Criteria: target function 

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-11-30
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 2.0: 2019-12-25
    Changes: Database references, Derived calculations, Polymer sequence, Source and taxonomy