Journal Article

Structure of the human frataxin-bound iron-sulfur cluster assembly complex provides insight into its activation mechanism

Feng, Xidong, Bailey, Henry J., Strain-Damerell, Claire, Bulawa, Christine, Martelli, Alain, Fox, Nicholas G., Yu, Xiaodi, Nabhan, Joseph F., Yue, Wyatt W., Han, Seungil

2019

Overview

The core machinery for de novo biosynthesis of iron-sulfur clusters (ISC), located in the mitochondria matrix, is a five-protein complex containing the cysteine desulfurase NFS1 that is activated by frataxin (FXN), scaffold protein ISCU, accessory protein ISD11, and acyl-carrier protein ACP. Deficiency in FXN leads to the loss-of-function neurodegenerative disorder Friedreich’s ataxia (FRDA). Here the 3.2 Å resolution cryo-electron microscopy structure of the FXN-bound active human complex, containing two copies of the NFS1-ISD11-ACP-ISCU-FXN hetero-pentamer, delineates the interactions of FXN with other component proteins of the complex. FXN binds at the interface of two NFS1 and one ISCU subunits, modifying the local environment of a bound zinc ion that would otherwise inhibit NFS1 activity in complexes without FXN. Our structure reveals how FXN facilitates ISC production through stabilizing key loop conformations of NFS1 and ISCU at the protein–protein interfaces, and suggests how FRDA clinical mutations affect complex formation and FXN activation. The iron-sulfur cluster (ISC) assembly complex is activated by frataxin (FXN) and Friedreich’s ataxia is caused by FXN deficiency. Here the authors present the 3.2 Å resolution cryo-EM structure of the human frataxin bound ISC complex and discuss how FXN activates enzymatic activity.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 101/28 / 101/58 / 631/45/173 / 631/535/1258/1259 / 631/535/1261 / 82/80 / 82/83 / Activation / Ataxia / Biosynthesis / Carbon-Sulfur Lyases - isolation & purification / Carbon-Sulfur Lyases - metabolism / Carbon-Sulfur Lyases - ultrastructure / Complex formation / Cryoelectron Microscopy / Electron microscopy / Enzymatic activity / Frataxin / Friedreich Ataxia - genetics / Friedreich Ataxia - pathology / Humanities and Social Sciences / Interfaces / Iron / Iron - metabolism / Iron-Binding Proteins - isolation & purification / Iron-Binding Proteins - metabolism / Iron-Binding Proteins - ultrastructure / Iron-Sulfur Proteins - isolation & purification / Iron-Sulfur Proteins - metabolism / Iron-Sulfur Proteins - ultrastructure / Mitochondria / Mitochondria - metabolism / Mitochondria - ultrastructure / Models, Molecular / multidisciplinary / Mutation / Neurodegenerative diseases / Protein deficiency / Proteins / Recombinant Proteins - isolation & purification / Recombinant Proteins - metabolism / Recombinant Proteins - ultrastructure / Science / Science (multidisciplinary) / Sulfur / Sulfur - metabolism / Zinc - metabolism