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Evidence for dynamic in vivo interconversion of the conformational states of IscU during iron–sulfur cluster biosynthesis
Author(s) -
Sato Sakiko,
Matsushima Yumeka,
Kanazawa Miaki,
Tanaka Naoyuki,
Fujishiro Takashi,
Kunichika Kouhei,
Nakamura Ryosuke,
Tomioka Hiroaki,
Wada Kei,
Takahashi Yasuhiro
Publication year - 2021
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14646
Subject(s) - biology , chaperone (clinical) , in vivo , iron–sulfur cluster , biochemistry , protein structure , biosynthesis , microbiology and biotechnology , biophysics , genetics , enzyme , medicine , pathology
Abstract IscU is a central component of the ISC machinery and serves as a scaffold for de novo assembly of Fe–S clusters. The dedicated chaperone system composed of the Hsp70‐chaperone HscA and the J‐protein cochaperone HscB synergistically interacts with IscU and facilitates cluster transfer from IscU to recipient apo‐proteins. Here, we report that the otherwise essential roles of HscA and HscB can be bypassed in vivo by a number of single amino acid substitutions in IscU. CD spectroscopic studies of the variant IscU proteins capable of this bypass activity revealed dynamic interconversion between two conformations: the denatured (D) and the structured (S) state in the absence and presence of Zn 2+ , respectively, which was far more prominent than interconversion observed in wild‐type IscU. Furthermore, we found that neither the S‐shifted (more structured) variants of IscU nor the perpetually denatured variants could perform their in vivo role regardless of whether the chaperone system was present or not. The present study thus provides for the first time evidence that an in vivo D‐state of IscU exists and implies that conformational interconversion between the S‐ and D‐states of the scaffolding protein is a fundamental requirement for the assembly and transfer of the Fe–S cluster.