From Proteopediaproteopedia link
Crystal structure of HLA-DQ0602 in complex with a hypocretin peptide
[OREX_HUMAN] Defects in HCRT are the cause of narcolepsy type 1 (NRCLP1) [MIM:161400]. Narcolepsy is a neurological disabling sleep disorder, characterized by excessive daytime sleepiness, sleep fragmentation, symptoms of abnormal rapid-eye-movement (REM) sleep, such as cataplexy, hypnagogic hallucinations, and sleep paralysis. Cataplexy is a sudden loss of muscle tone triggered by emotions, which is the most valuable clinical feature used to diagnose narcolepsy. Human narcolepsy is primarily a sporadically occurring disorder but familial clustering has been observed. Note=Human narcolepsy is associated with a deficient orexin system. Orexins are absent and/or greatly diminished in the brain and cerebrospinal fluid (CSF) of most narcoleptic patients.
[OREX_HUMAN] Neuropeptides that play a significant role in the regulation of food intake and sleep-wakefulness, possibly by coordinating the complex behavioral and physiologic responses of these complementary homeostatic functions. A broader role in the homeostatic regulation of energy metabolism, autonomic function, hormonal balance and the regulation of body fluids, is also suggested. Orexin-A binds to both OX1R and OX2R with a high affinity, whereas orexin-B binds only to OX2R with a similar high affinity.
Publication Abstract from PubMed
The MHC class II molecule DQ0602 confers strong susceptibility to narcolepsy but dominant protection against type 1 diabetes. The crystal structure of DQ0602 reveals the molecular features underlying these contrasting genetic properties. Structural comparisons to homologous DQ molecules with differential disease associations highlight a previously unrecognized interplay between the volume of the P6 pocket and the specificity of the P9 pocket, which implies that presentation of an expanded peptide repertoire is critical for dominant protection against type 1 diabetes. In narcolepsy, the volume of the P4 pocket appears central to the susceptibility, suggesting that the presentation of a specific peptide population plays a major role.
Crystal structure of HLA-DQ0602 that protects against type 1 diabetes and confers strong susceptibility to narcolepsy.,Siebold C, Hansen BE, Wyer JR, Harlos K, Esnouf RE, Svejgaard A, Bell JI, Strominger JL, Jones EY, Fugger L Proc Natl Acad Sci U S A. 2004 Feb 17;101(7):1999-2004. Epub 2004 Feb 9. PMID:14769912
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.