{"title":"SmsB-SmsC machinery in <i>Thermococcus kodakarensis</i> functions as an archaeal scaffold mediating Fe-S cluster assembly.","authors":"Jian-Qiang Jin, Takaaki Sato, Haruyuki Atomi","doi":"10.1128/aem.01438-25","DOIUrl":null,"url":null,"abstract":"<p><p>The SUF system is one of the multiprotein machineries responsible for iron-sulfur (Fe-S) cluster biogenesis. In bacterial and eukaryotic SUF systems, SufB, SufC, and SufD form a SufBC<sub>2</sub>D complex as the scaffold for Fe-S cluster assembly. SMS (SUF-like minimal system), composed only of SufB and SufC homologs (SmsB and SmsC) without a SufD component, has recently been established, and representatives from methanogenic archaea have been experimentally verified to function in Fe-S cluster biogenesis. SMS has been proposed to be an ancestor of the SUF system. The hyperthermophilic archaeon <i>Thermococcus kodakarensis</i> harbors candidate proteins for SmsB and SmsC (<i>Tk</i>-SmsB and <i>Tk</i>-SmsC) encoded by TK0730 and TK0731 genes, respectively. As <i>Tk</i>-SmsB is phylogenetically positioned in a clade distinct from the previously characterized SmsB proteins from methanogens, here, we examined whether <i>Tk</i>-SmsB and <i>Tk</i>-SmsC can also function in Fe-S cluster generation and transfer. <i>Tk</i>-SmsB and <i>Tk</i>-SmsC formed a heterotetrameric SmsB<sub>2</sub>C<sub>2</sub> complex. <i>Tk</i>-SmsC displayed ATPase activity, and its catalytic efficiency (<i>k</i><sub>cat</sub>/<i>K</i><sub>m</sub>) increased up to 10-fold upon complex formation with <i>Tk</i>-SmsB. The <i>Tk</i>-SmsB<sub>2</sub>C<sub>2</sub> complex could generate Fe-S clusters in the presence of ferric and sulfide ions. The holo-<i>Tk</i>-SmsB<sub>2</sub>C<sub>2</sub> complex could transfer the Fe-S clusters to the apo-form of the Fe-S cluster-dependent lipoyl synthase LipS from <i>T. kodakarensis</i>, resulting in a LipS with sulfur insertion activity for lipoyl group biosynthesis. In the presence of cysteine desulfurase and ATP, the apo-<i>Tk</i>-SmsB<sub>2</sub>C<sub>2</sub> complex could also generate Fe-S clusters utilizing cysteine as a sulfur donor and activate LipS.IMPORTANCEA representative of an SmsB protein from <i>T. kodakarensis</i> (<i>Tk</i>-SmsB) that lies in a clade phylogenetically distinct from those of previously verified SmsB proteins has been examined. The results demonstrate that <i>Tk</i>-SmsB, along with <i>Tk</i>-SmsC, functions as a scaffold for Fe-S cluster synthesis in <i>T. kodakarensis</i>, adding further support to the proposition that SMS represents the primitive form of the SUF systems widely present in bacteria and eukaryotes.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0143825"},"PeriodicalIF":3.7000,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12442378/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Applied and Environmental Microbiology","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1128/aem.01438-25","RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/8/18 0:00:00","PubModel":"Epub","JCR":"Q2","JCRName":"BIOTECHNOLOGY & APPLIED MICROBIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
The SUF system is one of the multiprotein machineries responsible for iron-sulfur (Fe-S) cluster biogenesis. In bacterial and eukaryotic SUF systems, SufB, SufC, and SufD form a SufBC2D complex as the scaffold for Fe-S cluster assembly. SMS (SUF-like minimal system), composed only of SufB and SufC homologs (SmsB and SmsC) without a SufD component, has recently been established, and representatives from methanogenic archaea have been experimentally verified to function in Fe-S cluster biogenesis. SMS has been proposed to be an ancestor of the SUF system. The hyperthermophilic archaeon Thermococcus kodakarensis harbors candidate proteins for SmsB and SmsC (Tk-SmsB and Tk-SmsC) encoded by TK0730 and TK0731 genes, respectively. As Tk-SmsB is phylogenetically positioned in a clade distinct from the previously characterized SmsB proteins from methanogens, here, we examined whether Tk-SmsB and Tk-SmsC can also function in Fe-S cluster generation and transfer. Tk-SmsB and Tk-SmsC formed a heterotetrameric SmsB2C2 complex. Tk-SmsC displayed ATPase activity, and its catalytic efficiency (kcat/Km) increased up to 10-fold upon complex formation with Tk-SmsB. The Tk-SmsB2C2 complex could generate Fe-S clusters in the presence of ferric and sulfide ions. The holo-Tk-SmsB2C2 complex could transfer the Fe-S clusters to the apo-form of the Fe-S cluster-dependent lipoyl synthase LipS from T. kodakarensis, resulting in a LipS with sulfur insertion activity for lipoyl group biosynthesis. In the presence of cysteine desulfurase and ATP, the apo-Tk-SmsB2C2 complex could also generate Fe-S clusters utilizing cysteine as a sulfur donor and activate LipS.IMPORTANCEA representative of an SmsB protein from T. kodakarensis (Tk-SmsB) that lies in a clade phylogenetically distinct from those of previously verified SmsB proteins has been examined. The results demonstrate that Tk-SmsB, along with Tk-SmsC, functions as a scaffold for Fe-S cluster synthesis in T. kodakarensis, adding further support to the proposition that SMS represents the primitive form of the SUF systems widely present in bacteria and eukaryotes.
期刊介绍：
Applied and Environmental Microbiology (AEM) publishes papers that make significant contributions to (a) applied microbiology, including biotechnology, protein engineering, bioremediation, and food microbiology, (b) microbial ecology, including environmental, organismic, and genomic microbiology, and (c) interdisciplinary microbiology, including invertebrate microbiology, plant microbiology, aquatic microbiology, and geomicrobiology.
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