Gene Group: MITOCHONDRIAL COMPLEX I SUBUNITS

General Information

Name

MITOCHONDRIAL COMPLEX I SUBUNITS

Species

D. melanogaster

Symbol

MCI

FlyBase ID

FBgg0000487

Date last reviewed

2024-09-16

Number of members

Description

Mitochondrial Complex I is the first and largest holoenzyme of the mitochondrial electron transport chain. It oxidizes NADH from the tricarboxylic acid cycle and β oxidation of fatty acids, reduces ubiquinone and transports protons across the inner membrane, contributing to the proton-motive force. It is also involved in the cellular production of reactive oxygen species. Fourteen distinct subunits form the catalytic centers of the enzyme as they are directly involved in transferring electrons from NADH to ubiquinone, or for generation of the membrane potential - they are referred to as the 'core' or 'central' subunits and are conserved from the ancestral enzyme in bacteria to mammals. Seven core subunits are encoded by mtDNA, while the others are encoded the nuclear genome. The remaining subunits are all encoded by nuclear DNA and are referred to as 'accessory' or 'supernumerary' subunits as they are not directly involved in catalysis. (Adapted from PMID:23527692 and FBrf0244962.)

Notes on Group

The division between 'CORE' and 'ACCESSORY' Complex I subunits in FlyBase follows that given in FBrf0244962.

Although initially isolated as part of Complex I (CI), the NDUFA4 subunit (encoded by ND-MLRQ, CG32230) is no longer considered a CI subunit, as several reports have established that it is a CIV subunit (FBrf0244962).

Readily identifiable orthologs of mammalian NDUFA3 and NDUFC1 are not found in Drosophila (FBrf0244962). However, a subunit matching mammalian NDUFA3 was detected by mass spectrometry in the purified D. melanogaster complex I (FBrf0255922).

The ND-B8 (NDUFA2) protein, which is present as a supernumerary subunit of mammalian complex I, is absent from purified Drosophila complex I. Moreover, ND-B8 expression is restricted principally to the male germline, suggesting the protein is unlikely to be a constitutive component of complex I in somatic tissues. (FBrf0255922)

Several nuclear genes encoding Complex I subunits exist as paralogs in D. melanogaster: ND-49 and ND-49L; ND-20 and ND-20L; ND-51, ND-51L1 and ND-51L2; ND-24 and ND-24L; ND-B14.5A and ND-B14.5AL; ND-AGGG and CG40472. In most cases, one paralog has widespread expression whereas the other is restricted to the testis. In addition, CG11815 and CG12464 have the same InterPro domain (IPR026193) as CG11752 (a NDUFV3 ortholog, FBrf0244962), but no there is no other orthology/literature evidence suggesting they are subunits of Complex I - CG11815 and CG12464 are therefore not included in this group.

Source Material

The MITOCHONDRIAL COMPLEX I SUBUNITS Gene Group has been compiled using the following publication(s): Agip et al., 2023, Rhooms et al., 2020, Garcia et al., 2017, Porcelli and Marygold, 2014.9.16, Porcelli et al., 2007, Caggese et al., 2006, Tripoli et al., 2005, and Fearnley and Walker, 1992 .

Key Gene Ontology (GO) terms

Molecular Function

NADH dehydrogenase (ubiquinone) activity

Biological Process

mitochondrial electron transport, NADH to ubiquinone

Cellular Component

respiratory chain complex I

mitochondrial inner membrane

Enzymatic activity

Enzyme name (EC)

NADH:ubiquinone reductase (H(+)-translocating) (7.1.1.2)

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