5w6m
From Proteopedia
Crystal structure of the human histidyl-tRNA synthetase mutant D175E
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 PubMedAminoacyl-transfer RNA (tRNA) synthetases (aaRSs) are the largest protein family causatively linked to neurodegenerative Charcot-Marie-Tooth (CMT) disease. Dominant mutations cause the disease, and studies of CMT disease-causing mutant glycyl-tRNA synthetase (GlyRS) and tyrosyl-tRNA synthetase (TyrRS) showed their mutations create neomorphic structures consistent with a gain-of-function mechanism. In contrast, based on a haploid yeast model, loss of aminoacylation function was reported for CMT disease mutants in histidyl-tRNA synthetase (HisRS). However, neither that nor prior work of any CMT disease-causing aaRS investigated the aminoacylation status of tRNAs in the cellular milieu of actual patients. Using an assay that interrogated aminoacylation levels in patient cells, we investigated a HisRS-linked CMT disease family with the most severe disease phenotype. Strikingly, no difference in charged tRNA levels between normal and diseased family members was found. In confirmation, recombinant versions of 4 other HisRS CMT disease-causing mutants showed no correlation between activity loss in vitro and severity of phenotype in vivo. Indeed, a mutation having the most detrimental impact on activity was associated with a mild disease phenotype. In further work, using 3 independent biophysical analyses, structural opening (relaxation) of mutant HisRSs at the dimer interface best correlated with disease severity. In fact, the HisRS mutation in the severely afflicted patient family caused the largest degree of structural relaxation. These data suggest that HisRS-linked CMT disease arises from open conformation-induced mechanisms distinct from loss of aminoacylation. CMT disease severity correlates with mutation-induced open conformation of histidyl-tRNA synthetase, not aminoacylation loss, in patient cells.,Blocquel D, Sun L, Matuszek Z, Li S, Weber T, Kuhle B, Kooi G, Wei N, Baets J, Pan T, Schimmel P, Yang XL Proc Natl Acad Sci U S A. 2019 Sep 24;116(39):19440-19448. doi:, 10.1073/pnas.1908288116. Epub 2019 Sep 9. PMID:31501329[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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