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TIMM50
translocase of inner mitochondrial membrane 50
TIMM50 is located on the long (q) arm of chromosome 19, at band 19q13.2. Arm ratio per GRCh38 - banding schematic.
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Overview
TIMM50 encodes the translocase of inner mitochondrial membrane 50, a core component of the protein import machinery within mitochondria. Mitochondria produce most of the cell's energy through oxidative phosphorylation, but nearly all mitochondrial proteins are synthesised in the cytoplasm and must be imported through specialised channels. TIMM50 acts as a receptor and scaffolding protein within the TIM23 complex, which translocates proteins across the inner mitochondrial membrane. When TIMM50 function is compromised, cells cannot maintain adequate mitochondrial protein levels, leading to impaired energy production and cellular dysfunction. Tissues with high energy demands, particularly the brain, are especially vulnerable to TIMM50 deficiency.
What the gene does
The TIMM50 protein serves two critical roles in mitochondrial protein import. First, it acts as a receptor for preproteins emerging from the outer membrane translocase, recognising targeting signals and facilitating handover to the inner membrane channel. Second, TIMM50 provides structural stability to the TIM23 complex, anchoring other subunits and coordinating the import process with the mitochondrial matrix machinery. The protein spans the inner mitochondrial membrane with its active regions extending into the intermembrane space, where it interacts with incoming preproteins. This import pathway is essential for assembling respiratory chain complexes, metabolic enzymes, and regulatory proteins within the mitochondrial matrix. Without functional TIMM50, mitochondria accumulate protein import defects that compromise multiple metabolic pathways simultaneously, affecting cellular respiration, amino acid metabolism, and oxidative stress responses.
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Chromosome location
TIMM50 is located on chromosome 19 at band q13.2. The gene spans approximately 12 kilobases of genomic DNA and contains seven exons. This chromosomal region contains numerous genes involved in cellular metabolism and protein trafficking, though TIMM50 is not part of a larger gene cluster. The genomic architecture is relatively compact compared to many mitochondrial genes.
Protein structure
The TIMM50 protein comprises 353 amino acids with a molecular weight of approximately 40 kilodaltons. The structure includes a disordered region spanning amino acids 25-60, which may provide flexibility for protein-protein interactions during the import process. The FCP1 homology domain extends from amino acids 143-286, representing the core functional region responsible for binding preproteins and coordinating with other TIM23 components. This domain architecture allows TIMM50 to function both as a receptor and a structural scaffold within the inner membrane translocase complex.
Key variants
Pathogenic variants in TIMM50 follow an autosomal recessive inheritance pattern, meaning affected individuals typically carry variants on both gene copies. The variant spectrum includes missense changes within the FCP1 homology domain that impair protein binding, as well as nonsense and frameshift variants that produce truncated, non-functional proteins. Most reported variants cluster in functionally critical regions essential for maintaining the structural integrity of the TIM23 complex.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
TIMM50-related disorders manifest as severe mitochondrial encephalomyopathies characterised by early-onset neurological regression, seizures, and metabolic decompensation. Affected individuals typically present in infancy or early childhood with developmental delay, hypotonia, and progressive neurological decline. The condition often includes intellectual disability, treatment-resistant epilepsy, and signs of generalised mitochondrial dysfunction such as lactic acidosis. Biochemical investigations may reveal deficiencies in multiple respiratory chain complexes, reflecting the gene's role in importing proteins essential for oxidative phosphorylation. The severity reflects the central importance of protein import to mitochondrial function across all tissues.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic TIMM50 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
Within the NHS Genomic Medicine Service, TIMM50 appears on multiple green-rated gene panels reflecting its clinical significance in mitochondrial and neurological disorders. The gene is included on the Early Onset or Syndromic Epilepsy panel (R59), Intellectual Disability panel (R29), Likely Inborn Error of Metabolism panel (R98), Mitochondrial Disorders panel, and Possible Mitochondrial Disorder - Nuclear Genes panel (R63). Green classification indicates strong evidence supporting the gene-disease relationship and suitability for diagnostic testing in relevant clinical presentations. Genetic testing for TIMM50 variants is typically considered when clinical features suggest mitochondrial dysfunction with prominent neurological involvement.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the TIMM50 protein do?
TIMM50 functions as both a receptor and structural component of the TIM23 complex, which transports newly synthesised proteins across the inner mitochondrial membrane. This import process is essential for assembling the hundreds of different proteins mitochondria need to generate cellular energy and perform metabolic functions.
How are TIMM50 variants inherited?
TIMM50 variants follow an autosomal recessive inheritance pattern. This means an individual must inherit a pathogenic variant from both parents to develop the associated condition. Carriers with one variant copy typically remain unaffected.
Why does TIMM50 deficiency primarily affect the brain?
The brain has exceptionally high energy demands and relies heavily on efficient mitochondrial function. When TIMM50 variants impair protein import, neurons cannot maintain adequate energy production or metabolic homeostasis, leading to the prominent neurological features observed in affected individuals.