4phc
From Proteopedia
Crystal Structure of a human cytosolic histidyl-tRNA synthetase, histidine-bound
Structural highlights
Disease[SYHC_HUMAN] Defects in HARS are a cause of Usher syndrome type 3B (USH3B) [MIM:614504]. USH3B is a syndrome characterized by progressive vision and hearing loss during early childhood. Some patients have the so-called 'Charles Bonnet syndrome,' involving decreased visual acuity and vivid visual hallucinations. USH is a genetically heterogeneous condition characterized by the association of retinitis pigmentosa with sensorineural deafness. Age at onset and differences in auditory and vestibular function distinguish Usher syndrome type 1 (USH1), Usher syndrome type 2 (USH2) and Usher syndrome type 3 (USH3). USH3 is characterized by postlingual, progressive hearing loss, variable vestibular dysfunction, and onset of retinitis pigmentosa symptoms, including nyctalopia, constriction of the visual fields, and loss of central visual acuity, usually by the second decade of life.[1] Note=HARS mutations may be involved in peripheral neuropathy, a disease mainly characterized by distal motor and sensory dysfunction. Inherited peripheral neuropathies are clinically and genetically heterogeneous with variable age of onset and reduced penetrance associated with specific loci. HARS mutations may directly predispose patients to peripheral neuropathy or may modify a peripheral neuropathy phenotype by contributing to the genetic and environmental load in a given patient (PubMed:22930593). Publication Abstract from PubMedAs part of a project aimed at obtaining selective inhibitors and drug-like compounds targeting tRNA synthetases from trypanosomatids, we have elucidated the crystal structure of human cytosolic histidyl-tRNA synthetase (Hs-cHisRS) in complex with histidine in order to be able to compare human and parasite enzymes. The resultant structure of Hs-cHisRS*His represents the substrate-bound state (H-state) of the enzyme. It provides an interesting opportunity to compare with ligand-free and imidazole-bound structures Hs-cHisRS published recently, both of which represent the ligand-free state (F-state) of the enzyme. The H-state Hs-cHisRS undergoes conformational changes in active site residues and several conserved motif of HisRS, compared to F-state structures. The histidine forms eight hydrogen bonds with HisRS of which six engage the amino and carboxylate groups of this amino acid. The availability of published imidazole-bound structure provides a unique opportunity to dissect the structural roles of individual chemical groups of histidine. The analysis revealed the importance of the amino and carboxylate groups, of the histidine in leading to these dramatic conformational changes of the H-state. Further, comparison with previously published trypanosomatid HisRS structures reveals a pocket in the F-state of the parasite enzyme that may provide opportunities for developing specific inhibitors of Trypanosoma brucei HisRS. Comparison of histidine recognition in human and trypanosomatid histidyl-tRNA synthetases.,Koh CY, Wetzel AB, de van der Schueren WJ, Hol WG Biochimie. 2014 Nov;106:111-20. doi: 10.1016/j.biochi.2014.08.005. Epub 2014 Aug , 20. PMID:25151410[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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