The 24-kDa iron-sulphur subunit of complex I is required for enzyme activity

• Type: Article in International Scientific Journal
• Date: 1999

Authors

almeida, t (Author) Other; duarte, m (Author) Other; melo, amp (Author) Other; videira, a (Author) ICBAS

Journal

Title: European Journal of Biochemistry

Vol. 265

Pages: 86-92

ISSN: 0014-2956

Publisher: Blackwell

Indexing

ISI Web of Knowledge - 22 Citations

Scopus - 21 Citations

Other information

Authenticus ID: P-001-35K

DOI: 10.1046/j.1432-1327.1999.00668.x

Abstract (EN): We have cloned the nuclear gene encoding the 24-kDa iron-sulphur subunit of complex I from Neurospora crassa. The gene was inactivated in vivo by repeat-induced point-mutations, and mutant strains lacking the 24-kDa protein were isolated. Mutant nuo24 appears to assemble an almost intact complex I only lacking the 24-kDa subunit. However, we also found reduced levels of the NADH-binding, 51-kDa subunit of the enzyme. Surprisingly, the complex I from the nuo24 strain lacks NADH:ferricyanide reductase activity. In agreement with this, the respiration of intact mitochondria or mitochondrial membranes from the mutant strain is insensitive to rotenone inhibition. These results suggest that the nuo24 complex is not functioning in electron transfer and the 24-kDa protein is absolutely required for complex I activity. This phenotype may explain the findings that the 24-kDa iron-sulphur protein is reduced or absent in human mitochondrial diseases. In addition, selected substitutions of cysteine to alanine residues in the 24-kDa protein suggest that binding of the iron-sulphur centre is a requisite for protein assembly.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7