# NDUFAF3

## Overview
NDUFAF3 is a gene that encodes the protein NADH:ubiquinone oxidoreductase complex assembly factor 3, which is crucial for the assembly of mitochondrial complex I, a key component of the mitochondrial respiratory chain involved in cellular energy production. The protein, localized in the mitochondrial inner membrane, interacts with other proteins to facilitate the integration and stability of complex I subunits. Mutations in the NDUFAF3 gene are linked to severe mitochondrial disorders, underscoring its essential role in mitochondrial function and energy metabolism. The protein's involvement in the early stages of complex I assembly and its dependency on mitochondrial translation highlight its fundamental biological importance (Saada2009Mutations).

## Structure
The molecular structure of the NDUFAF3 protein has been partially elucidated through homology modeling, using a protein with unknown function (PDB code 2FVT) that shares 30% sequence identity with NDUFAF3 over a stretch of 129 amino acids. This model has provided insights into the potential structural impacts of specific mutations on the protein. For instance, the G77R mutation is located in a conserved region where Gly77 has backbone-torsion angles that are unfavorable for other residue types, suggesting that this mutation disrupts the protein structure by being energetically unfavorable. Another mutation, R122P, is predicted to alter the structure of a loop at the C-terminal side of the protein, which could affect protein interactions or stability (Saada2009Mutations).

Additionally, the model reveals a large hydrophobic domain within NDUFAF3, which is typical for facilitating protein-protein interactions. The visualization of the protein in a ribbon model, colored by secondary structure elements, provides further insights into the secondary and tertiary structure of NDUFAF3, highlighting the presence of beta strands, alpha helices, turns, and coils (Saada2009Mutations).

## Function
NDUFAF3, also known as C3ORF60, is a mitochondrial protein that plays a pivotal role in the assembly of complex I, a fundamental component of the mitochondrial respiratory chain essential for cellular energy production. This protein is involved in the early stages of complex I assembly, particularly in association with other proteins such as NDUFAF4, NDUFS2, NDUFS3, NDUFS8, and NDUFA5, which are crucial for the proper functioning and structural integrity of complex I (Saada2009Mutations). NDUFAF3 and NDUFAF4 are codependent and localize in the mitochondrial inner membrane, participating in at least three previously described assembly intermediates (Saada2009Mutations).

The function of NDUFAF3 is closely related to mitochondrial translation, as it is required for the association of mitochondrial DNA-encoded ND subunits into higher-molecular-weight complexes of complex I. Inhibition of mitochondrial translation leads to a disruption in the incorporation of NDUFAF3 into these complexes, highlighting its dependency on this process for proper function (Saada2009Mutations). Additionally, gene-order-conservation analysis suggests that NDUFAF3's function in complex I assembly may be evolutionarily conserved from its bacterial ancestors, indicating a fundamental role in mitochondrial protein assembly and function (Saada2009Mutations).

## Clinical Significance
Mutations in the NDUFAF3 gene are associated with a fatal neonatal mitochondrial disease characterized by severe mitochondrial complex I deficiency. This condition manifests shortly after birth with symptoms including lactic acidemia, increased muscle tone, macrocephaly, severe muscle weakness, hypotonia, and diffuse leukomalacia. These clinical manifestations lead to a rapid deterioration in health, resulting in death before the age of six months (Saada2009Mutations). 

The NDUFAF3 gene plays a crucial role in the assembly of mitochondrial complex I, a key component of the mitochondrial respiratory chain essential for ATP production. Mutations in NDUFAF3 disrupt this assembly process, leading to diminished complex I activity and severe metabolic disorders (Saada2009Mutations). 

Experimental evidence further supports the critical role of NDUFAF3 in mitochondrial function. Fibroblasts from patients with specific NDUFAF3 mutations exhibit decreased levels of complex I subunits and impaired complex I activity. Complementation studies with NDUFAF3-GFP in these fibroblasts restored complex I activity, confirming the gene's essential role in maintaining mitochondrial complex I integrity (Saada2009Mutations).

## Interactions
NDUFAF3, encoded by the NDUFAF3 gene, is a mitochondrial complex I assembly protein that interacts with several other proteins crucial for the assembly and function of mitochondrial complex I. It forms a codependent relationship with NDUFAF4, another complex I assembly protein. The interaction between NDUFAF3 and NDUFAF4 is essential for the assembly process, as evidenced by the decrease in NDUFAF3 protein levels following RNA interference for NDUFAF4 (Saada2009Mutations). This interaction also involves the localization of both proteins in the mitochondrial inner membrane, participating in the assembly of complex I substructures including subunits NDUFS2, NDUFS3, NDUFS8, and NDUFA5 (Saada2009Mutations).

Furthermore, NDUFAF3 is involved in interactions with the core subunits of complex I, predominantly NDUFS2 and NDUFS3, as demonstrated through copurification studies using stable HEK293 Trex Flp-in clones containing TAP-tagged constructs of these proteins (Saada2009Mutations). These interactions are vital for the proper assembly and functionality of mitochondrial complex I, which plays a critical role in cellular energy production. The gene-order-conservation analysis also links NDUFAF3 to the Sec membrane-translocation machinery in alpha-proteobacteria, suggesting a role in coupling mitochondrial translation to membrane insertion during assembly (Saada2009Mutations).


## References


[1. (Saada2009Mutations) Ann Saada, Rutger O. Vogel, Saskia J. Hoefs, Mariël A. van den Brand, Hans J. Wessels, Peter H. Willems, Hanka Venselaar, Avraham Shaag, Flora Barghuti, Orit Reish, Mordechai Shohat, Martijn A. Huynen, Jan A.M. Smeitink, Lambert P. van den Heuvel, and Leo G. Nijtmans. Mutations in ndufaf3 (c3orf60), encoding an ndufaf4 (c6orf66)-interacting complex i assembly protein, cause fatal neonatal mitochondrial disease. The American Journal of Human Genetics, 84(6):718–727, June 2009. URL: http://dx.doi.org/10.1016/j.ajhg.2009.04.020, doi:10.1016/j.ajhg.2009.04.020. (199 citations) 10.1016/j.ajhg.2009.04.020](https://doi.org/10.1016/j.ajhg.2009.04.020)