scholarly journals IBA57 mutations abrogate iron-sulfur cluster assembly leading to cavitating leukoencephalopathy

2017 ◽  
Vol 3 (5) ◽  
pp. e184 ◽  
Author(s):  
Akihiko Ishiyama ◽  
Chika Sakai ◽  
Yuichi Matsushima ◽  
Satoru Noguchi ◽  
Satomi Mitsuhashi ◽  
...  
Keyword(s):  
Protein Expression ◽  
Lipoic Acid ◽  
Protein Assembly ◽  
Assembly System ◽  
Iron Sulfur Cluster ◽  
Sulfur Cluster ◽  
Iron Sulfur ◽  
Mitochondrial Iron ◽  
Sulfur Protein ◽  
Iron Sulfur Protein

Objective:To determine the molecular factors contributing to progressive cavitating leukoencephalopathy (PCL) to help resolve the underlying genotype-phenotype associations in the mitochondrial iron-sulfur cluster (ISC) assembly system.Methods:The subjects were 3 patients from 2 families who showed no inconsistencies in either clinical or brain MRI findings as PCL. We used exome sequencing, immunoblotting, and enzyme activity assays to establish a molecular diagnosis and determine the roles of ISC-associated factors in PCL.Results:We performed genetic analyses on these 3 patients and identified compound heterozygosity for the IBA57 gene, which encodes the mitochondrial iron-sulfur protein assembly factor. Protein expression analysis revealed substantial decreases in IBA57 protein expression in myoblasts and fibroblasts. Immunoblotting revealed substantially reduced expression of SDHB, a subunit of complex II, and lipoic acid synthetase (LIAS). Levels of pyruvate dehydrogenase complex-E2 and α-ketoglutarate dehydrogenase-E2, which use lipoic acid as a cofactor, were also reduced. In activity staining, SDH activity was clearly reduced, but it was ameliorated in mitochondrial fractions from rescued myoblasts. In addition, NFU1 protein expression was also decreased, which is required for the assembly of a subset of iron-sulfur proteins to SDH and LIAS in the mitochondrial ISC assembly system.Conclusions:Defects in IBA57 essentially regulate NFU1 expression, and aberrant NFU1 ultimately affects SDH activity and LIAS expression in the ISC biogenesis pathway. This study provides new insights into the role of the iron-sulfur protein assembly system in disorders related to mitochondrial energy metabolism associated with leukoencephalopathy with cavities.

scholarly journals Depletion of thiol reducing capacity impairs cytosolic but not mitochondrial iron-sulfur protein assembly machineries

2019 ◽  
Vol 1866 (2) ◽  
pp. 240-251 ◽  
Author(s):  
Joseph J. Braymer ◽  
Martin Stümpfig ◽  
Stefanie Thelen ◽  
Ulrich Mühlenhoff ◽  
Roland Lill
Keyword(s):  
Protein Assembly ◽  
Iron Sulfur ◽  
Mitochondrial Iron ◽  
Sulfur Protein ◽  
Iron Sulfur Protein ◽  
Reducing Capacity

Dependence of heme biosynthesis on iron-sulfur cluster biogenesis: human ALAD is an unrecognized iron-sulfur protein

2020 ◽  
Author(s):  
Gang Liu ◽  
Debangsu Sil ◽  
Wing-Hang Tong ◽  
Nunziata Maio ◽  
J. Martin Bollinger ◽  
...  
Keyword(s):  
Metabolic Pathways ◽  
Biosynthetic Pathway ◽  
Aminolevulinic Acid ◽  
Heme Biosynthesis ◽  
Second Step ◽  
Iron Sulfur Cluster ◽  
Sulfur Cluster ◽  
Iron Sulfur ◽  
Sulfur Protein ◽  
Iron Sulfur Protein

Abstract Heme biosynthesis and iron-sulfur cluster (ISC) biogenesis are two major mammalian metabolic pathways that require iron. It has long been known that these two pathways interconnect, but the previously described interactions do not fully explain why heme biosynthesis depends on intact ISC biogenesis. Herein we have identified a previously unrecognized connection between these two pathways through our discovery that human aminolevulinic acid dehydratase (ALAD), which catalyzes the second step of heme biosynthesis, is an Fe-S protein. We found that several highly conserved cysteines and an Ala306-Phe307-Arg308 motif of human ALAD are important for [Fe4S4] cluster acquisition and coordination. The enzymatic activity of human ALAD was greatly reduced upon loss of its Fe-S cluster, which resulted in reduced heme biosynthesis in human cells. Our findings explain why heme biosynthesis depends on intact ISC biogenesis, as ALAD provides an early Fe-S-dependent checkpoint in the heme biosynthetic pathway.

scholarly journals Structural Alterations of the Cysteine Desulfurase IscS of Salmonella enterica Serovar Typhimurium Reveal Substrate Specificity of IscS in tRNA Thiolation

2006 ◽  
Vol 188 (8) ◽  
pp. 3052-3062 ◽  
Author(s):  
Hans K. Lundgren ◽  
Glenn R. Björk
Keyword(s):  
Substrate Specificity ◽  
Salmonella Enterica ◽  
Cluster Formation ◽  
Cysteine Desulfurase ◽  
Iron Sulfur Cluster ◽  
Sulfur Cluster ◽  
Iron Sulfur ◽  
Serovar Typhimurium ◽  
Sulfur Protein ◽  
Iron Sulfur Protein

ABSTRACT The cysteine desulfurase IscS in Salmonella enterica serovar Typhimurium is required for the formation of all four thiolated nucleosides in tRNA, which is thought to occur via two principally different biosynthetic pathways. The synthesis of 4-thiouridine (s4U) and 5-methylaminomethyl-2-thiouridine (mnm5s2U) occurs by a transfer of sulfur from IscS via various proteins to the target nucleoside in the tRNA, and no iron-sulfur cluster protein participates, whereas the synthesis of 2-thiocytidine (s2C) and N 6-(4-hydroxyisopentenyl)-2-methylthioadenosine (ms2io6A) is dependent on iron-sulfur cluster proteins, whose formation and maintenance depend on IscS. Accordingly, inactivation of IscS should result in decreased synthesis of all thiolated nucleosides. We selected mutants defective either in the synthesis of a thiolated nucleoside (mnm5s2U) specific for the iron-sulfur protein-independent pathway or in the synthesis of a thiolated nucleoside (ms2io6A) specific for the iron-sulfur protein-dependent pathway. Although we found altered forms of IscS that influenced the synthesis of all thiolated nucleosides, consistent with the model, we also found mutants defective in subsets of thiolated nucleosides. Alterations in the C-terminal region of IscS reduced the level of only ms2io6A, suggesting that the synthesis of this nucleoside is especially sensitive to minor aberrations in iron-sulfur cluster transfer activity. Our results suggest that IscS has an intrinsic substrate specificity in how it mediates sulfur mobilization and/or iron-sulfur cluster formation and maintenance required for thiolation of tRNA.

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