1cq0
From Proteopedia
SOLUTION STRUCTURE OF A HUMAN HYPOCRETIN-2/OREXIN-B'SOLUTION STRUCTURE OF A HUMAN HYPOCRETIN-2/OREXIN-B '
Structural highlights
Disease[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.[1] Function[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 PubMedOrexin-A and orexin-B (also called hypocretin-1 and hypocretin-2, respectively) are novel hypothalamic neuropeptides encoded by a single mRNA transcript; they stimulate food intake. We have determined the three-dimensional solution structure of human hypocretin-2/orexin-B using two-dimensional 1H-NMR data and dynamical simulated annealing calculations. On the basis of NOEs, 3JHNalpha coupling constants and hydrogen-deuterium exchange rates together with chemical shift indices, human hypocretin-2/orexin-B was deduced to consist of two alpha-helices connected with a short linker in both H2O and 30% trifluoroethanol solutions. The helical axis of helix I is oriented about 60-80 degrees relative to helix II. Hybrid distance geometry and simulated-annealing protocols were used to generate an ensemble of 30 structures with no constraint violations greater than 0.03 nm for distances and 3 degrees for angles. In addition, human hypocretin-2/orexin-B shares a similar secondary-structural motif with human neuropeptide Y. This result can form the basis for further study on ligand-receptor recognition of human orexin receptors. Solution structure of a new hypothalamic neuropeptide, human hypocretin-2/orexin-B.,Lee JH, Bang E, Chae KJ, Kim JY, Lee DW, Lee W Eur J Biochem. 1999 Dec;266(3):831-9. PMID:10583376[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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