Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutations in the gene SURF1 prevent synthesis of cytochrome-c oxidase (COX)-specific assembly protein and result in a fatal neurological disorder, Leigh syndrome. Because this severe COX deficiency presents with barely detectable changes of cellular respiratory rates under normoxic conditions, we analyzed the respiratory response to low oxygen in cultured fibroblasts harboring SURF1 mutations with high-resolution respirometry. The oxygen kinetics was quantified by the partial pressure of oxygen (PO2) at half-maximal respiration rate (P50) in intact coupled cells and in digitonin-permeabilized uncoupled cells. In both cases, the P50 in patients was elevated 2.1- and 3.3-fold, respectively, indicating decreased affinity of COX for oxygen. These results suggest that at physiologically low intracellular PO2, the depressed oxygen affinity may lead in vivo to limitations of respiration, resulting in impaired energy provision in Leigh syndrome patients.
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PMID:Decreased affinity for oxygen of cytochrome-c oxidase in Leigh syndrome caused by SURF1 mutations. 1526 7

Mutations in SURF1, the human homologue of yeast SHY1, are responsible for Leigh's syndrome, a neuropathy associated with cytochrome oxidase (COX) deficiency. Previous studies of the yeast model of this disease showed that mutant forms of Mss51p, a translational activator of COX1 mRNA, partially rescue the COX deficiency of shy1 mutants by restoring normal synthesis of the mitochondrially encoded Cox1p subunit of COX. Here we present evidence showing that Cox1p synthesis is reduced in most COX mutants but is restored to that of wild type by the same mss51 mutation that suppresses shy1 mutants. An important exception is a null mutation in COX14, which by itself or in combination with other COX mutations does not affect Cox1p synthesis. Cox14p and Mss51p are shown to interact with newly synthesized Cox1p and with each other. We propose that the interaction of Mss51p and Cox14p with Cox1p to form a transient Cox14p-Cox1p-Mss51p complex functions to downregulate Cox1p synthesis. The release of Mss51p from the complex occurs at a downstream step in the assembly pathway, probably catalyzed by Shy1p.
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PMID:Mss51p and Cox14p jointly regulate mitochondrial Cox1p expression in Saccharomyces cerevisiae. 1530 53

Leigh syndrome with cytochrome oxidase (COX) deficiency has been associated with SURF1 mutations. For patient diagnosis, distinction between neutral polymorphisms and pathogenic missense SURF1 mutations in Leigh syndrome is essential. We show that several missense SURF1 mutations did not allow a stable protein to be expressed. Absence of immunologically reactive SURF1 is, therefore, helpful to demonstrate their pathogenicity. In addition, we show that out of two previously described missense mutations housed by the same allele, only one, the T737 C was pathogenic. Indeed, transfection of T737 C mutated SURF1 in SURF1-deficient cells did not restore normal SURF1 stability and COX activity. On the contrary, the G604 C-mutated SURF1 did it and, hence, is a neutral variant.
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PMID:Pathogenicity of missense mutations in SURF1 deficiency inducing the Leigh syndrome. Importance in diagnosis. 1612 Mar 73

The mitochondrial oxidative phosphorylation system is composed of five multiprotein complexes. The fourth complex of this system, cytochrome c oxidase (complex IV), consists of 13 subunits: 3 encoded by mitochondrial DNA and 10 encoded by the nuclear genome. Patients with an isolated complex IV deficiency frequently harbor mutations in nuclear genes encoding for proteins necessary for the assembly of the complex. Strikingly, until now, no mutations have been detected in the nuclear encoded structural subunits of complex IV in these patients. We report the results of a mutational analysis study in patients with isolated complex IV deficiency screened for mutations in all structural genes as well as assembly genes known to cause complex IV deficiency. Four patients carried mutations in the complex IV assembly gene SURF1. One patient harbored a mutation in the COX10 gene involved in heme A synthesis. Mutations in the 10 nuclear encoded structural genes were not present.
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PMID:Sequence analysis of the structural nuclear encoded subunits and assembly genes of cytochrome c oxidase in a cohort of 10 isolated complex IV-deficient patients revealed five mutations. 1694 36

Leigh syndrome is the most common mitochondrial disorder in children characterized by necrotic lesions in the central nervous system. Both mitochondrial DNA (mtDNA) and nuclear DNA defects in the mitochondrial respiratory chain can lead to this disease. To characterize the clinical and genetic traits of Leigh or Leigh-like syndrome patients in China, 124 unrelated cases were collected between 1992 and 2005. Seventy-seven cases (62.1%) met the typical criteria of Leigh syndrome, including symmetrical bilateral abnormal signals in the basal ganglia, thalamus and brain stem, etc. Other cases (37.9%) belonged to Leigh-like syndrome with atypical clinical or radiological manifestations. Late-onset patients accounted for 20.2%, which is more than previously reported. Movement disorder was the most common symptoms in our patients. Thirty-two patients (25.8%) were confirmed to carry mutant genes. Among them, six cases (4.8%) have been demonstrated to have point mutations in mitochondrial DNA. Two separate patients were detected to have mutations on A8344G and A3243G. The T8993G point mutation was identified in one patient and T8993C in one other patient. SURF1 mutations associated with cytochrome-c oxidase deficiency were identified in 25 patients (20.2%). Four unreported variations have been identified in SURF1 gene from three patients. G604C was found in 22 patients. Only one patient had C214T mutation in the pyruvate dehydrogenase E1alpha subunit gene. In the remaining 92 patients (74.2%), a specific molecular dysfunction or underlying metabolic abnormality could not be identified.
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PMID:Clinical and molecular survey in 124 Chinese patients with Leigh or Leigh-like syndrome. 1732 45

Cytochrome c oxidase (complex IV) of the respiratory chain is assembled from nuclear and mitochondrially-encoded subunits. Defects in the assembly process lead to severe human disorders such as Leigh syndrome. Shy1 is an assembly factor for complex IV in Saccharomyces cerevisiae and mutations of its human homolog, SURF1, are the most frequent cause for Leigh syndrome. We report that Shy1 promotes complex IV biogenesis through association with different protein modules; Shy1 interacts with Mss51 and Cox14, translational regulators of Cox1. Additionally, Shy1 associates with the subcomplexes of complex IV that are potential assembly intermediates. Formation of these subcomplexes depends on Coa1 (YIL157c), a novel assembly factor that cooperates with Shy1. Moreover, partially assembled forms of complex IV bound to Shy1 and Cox14 can associate with the bc1 complex to form transitional supercomplexes. We suggest that Shy1 links Cox1 translational regulation to complex IV assembly and supercomplex formation.
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PMID:Shy1 couples Cox1 translational regulation to cytochrome c oxidase assembly. 1788 59

Leigh syndrome is a common clinical manifestation in children with mitochondrial disease and other types of inborn errors of metabolism. We characterised clinical symptoms, prognosis, respiratory chain function and performed extensive genetic analysis of 25 Swedish children suffering from Leigh syndrome with the aim to obtain insights into the molecular pathophysiology and to provide a rationale for genetic counselling. We reviewed the clinical history of all patients and used muscle biopsies in order to perform molecular, biochemical and genetic investigations, including sequencing the entire mitochondrial DNA (mtDNA), the mitochondrial DNA polymerase (POLGA) gene and the surfeit locus protein 1 (SURF1) gene. Respiratory chain enzyme activity measurements identified five patients with isolated complex I deficiency and five with combined enzyme deficiencies. No patient presented with isolated complex IV deficiency. Seven patients had a decreased ATP production rate. Extensive sequence analysis identified eight patients with pathogenic mtDNA mutations and one patient with mutations in POLGA. Mutations of mtDNA are a common cause of LS and mtDNA analysis should always be included in the diagnosis of LS patients, whereas SURF1 mutations are not a common cause of LS in Sweden. Unexpectedly, age of onset, clinical symptoms and prognosis did not reveal any clear differences in LS patients with mtDNA or nuclear DNA mutations.
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PMID:MtDNA mutations are a common cause of severe disease phenotypes in children with Leigh syndrome. 1910 52

We report two patients with Leigh syndrome that showed a combination of facial dysmorphism and MRI imaging indicating an SURF1 deficiency, which was confirmed by sequence analysis. Case 1 is a 3-year-old girl with failure to thrive and developmental delay. She presented with tachypnea at rest and displayed facial dysmorphism including frontal bossing, lateral displacement of inner canthi, esotropia, maxillary hypoplasia, slightly upturned nostril, and hypertrichosis dominant on the forehead and extremities. Case 2 is an 8-year-old boy with respiratory failure. He had been diagnosed as selective complex IV deficiency. Case 2 displayed facial dysmorphism and hypertrichosis. Since both patients displayed characteristic facial dysmorphism and MRI findings, we sequenced the SURF1 gene and identified two heterozygous mutations; c.49+1 G>T and c.752_753del in Case 1, and homozygous c.743 C>A in Case 2. For patients with Leigh syndrome showing these facial dysmorphism and hypertrichosis, sequence analysis of the SURF1 gene may be useful.
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PMID:Two Japanese patients with Leigh syndrome caused by novel SURF1 mutations. 2241 Apr 71

Leigh syndrome (LS) is a mitochondrial disease that typically presents in infancy with subacute neurodegenerative encephalopathy. It is genetically heterogeneous, but mutations in the complex IV assembly genes, particularly SURF1, are an important cause. In this study, SURF1 gene was sequenced in 590 patients with clinical suspicion of LS, complex IV deficiency, or clinical features of mitochondrial disorders. We identified 21 patients with clinical features of LS who are either homozygous or compound heterozygous for SURF1 mutations. Twenty-two different mutations were identified, including 13 novel mutations. Of the 42 mutant alleles, 36 (86%) are null mutations (frameshift, splicing, or nonsense) and 6 (14%) are missense. We have also reviewed the previously reported SURF1 mutations and observed a clustering of mutation in exon 8 of SURF1, suggesting a vital function for this region. Although mutations in SURF1 have been mainly associated with typical LS, five of the patients in this report had an atypical course of LS. There is no definite genotype-phenotype correlation; however, frameshift mutations resulting in protein truncation closer to the C-terminus may carry a better prognosis.
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PMID:SURF1-associated Leigh syndrome: a case series and novel mutations. 2248 15

A multicenter comparison of mitochondrial respiratory chain and complex V enzyme activity tests was performed. The average reproducibility of the enzyme assays is 16% in human muscle samples. In a blinded diagnostic accuracy test in patient fibroblasts and SURF1 knock-out mouse muscle, each lab made the correct diagnosis except for two complex I results. We recommend that enzyme activities be evaluated based on ratios, e.g. with complex IV or citrate synthase activity. In spite of large variations in observed enzyme activities, we show that inter-laboratory comparison of patient sample test results is possible by using normalization against a control sample.
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PMID:A multi-center comparison of diagnostic methods for the biochemical evaluation of suspected mitochondrial disorders. 2316 99


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