The Eukaryotic P Loop NTPase Nbp35: An Essential Component of the Cytosolic and Nuclear Iron-Sulfur Protein Assembly Machinery

• Published in: Proceedings of the National Academy of Sciences - PNAS 2005-03, Vol.102 (9), p.3266-3271
• Main Authors: Hausmann, Anja, Daili J. Aguilar Netz, Balk, Janneke, Pierik, Antonio J., Mühlenhoff, Ulrich, Lill, Roland, Beinert, Helmut
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - metabolism; Adenosine Triphosphatases - physiology; Bacteria; Biochemistry; Biological Sciences; Cell growth; Cell Nucleus - metabolism; Cellular immunity; Cytosol; Cytosol - metabolism; Dehydrogenases; Enzymes; Eukaryotes; Eukaryotic cells; GTP-Binding Proteins - metabolism; GTP-Binding Proteins - physiology; Iron; Iron-Sulfur Proteins - metabolism; Mitochondria; Mitochondria - metabolism; Porins; Protein Binding; Proteins; Recombinant Proteins - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins - metabolism; Saccharomyces cerevisiae Proteins - physiology; Sulfur; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0406447102

Soluble P loop NTPases represent a large protein family and are involved in diverse cellular functions. Here, we functionally characterized the first member of the Mrp/Nbp35 subbranch of this family, the essential Nbp35p of Saccharomyces cerevisiae. The protein resides in the cytosol and nucleus and carries an Fe/S cluster at its N terminus. Assembly of the Fe/S cluster requires the mitochondrial Fe/S cluster (ISC)-assembly and -export machineries. Depletion of Nbp35p strongly impairs the activity of the cytosolic Fe/S protein, isopropylmalate isomerase (Leu1p), whereas mitochondrial Fe/S enzymes are unaffected. Moreover, defects in the de novo maturation of various cytosolic and nuclear Fe/S proteins were observed in the absence of Nbp35p, demonstrating the functional involvement of Nbp35p in the biogenesis of extramitochondrial Fe/S proteins. Furthermore, Nbp35p genetically interacts with the closely similar P loop NTPase, Cfd1p, and the hydrogenase-like Nar1p, both of which were recently shown to perform a crucial function in cytosolic and nuclear Fe/S protein biogenesis. Hence, our study suggests that eukaryotic Nbp35 NTPases function in Fe/S protein maturation. The findings provide strong evidence for the existence of a highly conserved and essential machinery dedicated to assembling cytosolic and nuclear Fe/S proteins.