Biology:SURF1

Generic protein structure example

Surfeit locus protein 1 (SURF1) is a protein that in humans is encoded by the SURF1 gene. The protein encoded by SURF1 is a component of the mitochondrial translation regulation assembly intermediate of cytochrome c oxidase complex (MITRAC complex), which is involved in the regulation of cytochrome c oxidase assembly. Defects in this gene are a cause of Leigh syndrome, a severe neurological disorder that is commonly associated with systemic cytochrome c oxidase (complex IV) deficiency, and Charcot-Marie-Tooth disease 4K (CMT4K).

Structure

SURF1 is located on the q arm of chromosome 9 in position 34.2 and has 9 exons. The SURF1 gene produces a 33.3 kDa protein composed of 300 amino acids. The protein is a member of the SURF1 family, which includes the related yeast protein SHY1 and rickettsial protein RP733. The gene is located in the surfeit gene cluster, a group of very tightly linked genes that do not share sequence similarity, where it shares a bidirectional promoter with SURF2 on the opposite strand. SURF1 is a multi-pass protein that contains two transmembrane regions, one 19 amino acids in length from positions 61-79 and the other 17 amino acids in length from positions 274-290.

Function

This gene encodes a protein localized to the inner mitochondrial membrane and thought to be involved in the biogenesis of the cytochrome c oxidase complex. SURF1 is a multi-pass membrane protein component of the mitochondrial translation regulation assembly intermediate of cytochrome c oxidase complex (MITRAC complex). The MITRAC complex regulates cytochrome c oxidase assembly by acting as a central assembly intermediate, receiving subunits imported to the inner mitochondrial membrane and regulating COX1 mRNA translation.

Clinical significance

Mutations in SURF1 have been associated with mitochondrial complex IV (cytochrome c oxidase) deficiency with clinical manifestations of Leigh syndrome and Charcot-Marie-Tooth disease 4K (CMT4K).

Mitochondrial complex IV deficiency

Mitochondrial complex IV deficiency is a disorder of the mitochondrial respiratory chain with heterogeneous clinical manifestations, ranging from isolated myopathy to severe multisystem disease affecting several tissues and organs. Features include hypertrophic cardiomyopathy, hepatomegaly and liver dysfunction, hypotonia, muscle weakness, exercise intolerance, developmental delay, delayed motor development and mental retardation. Some affected individuals manifest a fatal hypertrophic cardiomyopathy resulting in neonatal death. A subset of patients manifest Leigh syndrome. In patients presenting with pathogenic mutations resulting in dysfunctioning SURF1, cytochrome c oxidase activity is likely to be diminished in one or more types of tissues.

Leigh syndrome

Leigh syndrome is an early-onset progressive neurodegenerative disorder characterized by the presence of focal, bilateral lesions in one or more areas of the central nervous system including the brainstem, thalamus, basal ganglia, cerebellum and spinal cord. Clinical features depend on which areas of the central nervous system are involved and include subacute onset of psychomotor retardation, hypotonia, ataxia, weakness, vision loss, eye movement abnormalities, seizures, and dysphagia. There have been over 30 different mutations in SURF1 that have been associated with Leigh syndrome. These mutations, which comprise at least 10 missense or nonsense, 8 splice site, and 12 insertion or deletion mutations, are believed to be the result of dysfunctional SURF1 that results in Leigh syndrome and cytochrome c oxidase deficiency. The most common mutation is believed to be 312_321del 311_312insAT.

Charcot-Marie-Tooth disease 4K (CMT4K)

Charcot-Marie-Tooth disease 4K (CMT4K) is an autosomal recessive, demyelinating form of Charcot-Marie-Tooth disease, a disorder of the peripheral nervous system, characterized by progressive weakness and atrophy, initially of the peroneal muscles and later of the distal muscles of the arms. Charcot-Marie-Tooth disease is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathies (designated CMT1 when they are dominantly inherited) and primary peripheral axonal neuropathies (CMT2). Demyelinating neuropathies are characterized by severely reduced nerve conduction velocities (less than 38 m/sec), segmental demyelination and remyelination with onion bulb formations on nerve biopsy, slowly progressive distal muscle atrophy and weakness, absent deep tendon reflexes, and hollow feet. By convention, autosomal recessive forms of demyelinating Charcot-Marie-Tooth disease are designated CMT4. CMT4K patients manifest upper and lower limbs involvement. Some affected individuals have nystagmus, polyneuropathy, putaminal and periaqueductal lesions, and late-onset cerebellar ataxia. This disease, when associated with mutations in SURF1, has been found to be linked to cytochrome c oxidase deficiency. Variants associated with this CMT4K have included a homozygous splice site mutation, c.107-2A>G, a missense mutation, c.574C>T, and a deletion, c.799_800del.

Interactions

SURF1 has been shown to have 11 binary protein-protein interactions including 8 co-complex interactions. SURF1 interacts with COA3 as part of the mitochondrial translation regulation assembly intermediate of cytochrome c oxidase complex (MITRAC complex). PTGES3, SLC25A5, COX6C, COX14, COA1 have all also been found to interact with SURF1.

Further reading

• "Cytochrome c oxidase deficiency". American Journal of Medical Genetics 106 (1): 46–52. 2001. doi:10.1002/ajmg.1378. PMID 11579424. 
• "The Surf-1 and Surf-2 genes and their essential bidirectional promoter elements are conserved between mouse and human". DNA and Cell Biology 13 (11): 1117–26. November 1994. doi:10.1089/dna.1994.13.1117. PMID 7702754. 
• "The human Surfeit locus". Genomics 52 (1): 72–8. August 1998. doi:10.1006/geno.1998.5372. PMID 9740673. 
• "Expression and functional analysis of SURF1 in Leigh syndrome patients with cytochrome c oxidase deficiency". Human Molecular Genetics 8 (13): 2541–9. December 1999. doi:10.1093/hmg/8.13.2541. PMID 10556303. 
• "Two novel mutations of SURF1 in Leigh syndrome with cytochrome c oxidase deficiency". Human Genetics 105 (6): 560–3. December 1999. doi:10.1007/s004390051145. PMID 10647889. 
• "Missense mutations in SURF1 associated with deficient cytochrome c oxidase assembly in Leigh syndrome patients". Human Genetics 106 (2): 194–205. February 2000. doi:10.1007/s004390051028. PMID 10746561. 
• "Three novel SURF-1 mutations in Japanese patients with Leigh syndrome". Pediatric Neurology 26 (3): 196–200. March 2002. doi:10.1016/S0887-8994(01)00382-4. PMID 11955926. 
• "[A new missense mutation of 574C>T in the SURF1 gene--biochemical and molecular genetic study in seven children with Leigh syndrome]". Casopis Lekaru Ceskych 141 (20): 636–41. October 2002. PMID 12515039. 
• "Mutation screening in patients with isolated cytochrome c oxidase deficiency". Pediatric Research 53 (2): 224–30. February 2003. doi:10.1203/01.PDR.0000048100.91730.6A. PMID 12538779. 
• "Leigh Syndrome with COX deficiency and SURF1 gene mutations: MR imaging findings". AJNR. American Journal of Neuroradiology 24 (6): 1188–91. 2003. PMID 12812953. 
• "SURF1 gene mutations in three cases with Leigh syndrome and cytochrome c oxidase deficiency". Neurology 61 (7): 991–3. October 2003. doi:10.1212/01.wnl.0000082391.98672.0a. PMID 14557577. 
• "Cytochrome c oxidase subassemblies in fibroblast cultures from patients carrying mutations in COX10, SCO1, or SURF1". The Journal of Biological Chemistry 279 (9): 7462–9. February 2004. doi:10.1074/jbc.M309232200. PMID 14607829. 
• "Novel SURF1 mutation in a child with subacute encephalopathy and without the radiological features of Leigh Syndrome". American Journal of Medical Genetics. Part A 128A (2): 195–8. July 2004. doi:10.1002/ajmg.a.30073. PMID 15214016. 
• "Assembly of cytochrome-c oxidase in the absence of assembly protein Surf1p leads to loss of the active site heme". The Journal of Biological Chemistry 280 (18): 17652–6. May 2005. doi:10.1074/jbc.C500061200. PMID 15764605. 
• "Atypical amyoplasia congenita in an infant with Leigh syndrome: a mitochondrial cause of severe contractures?". American Journal of Medical Genetics. Part A 158A (9): 2353–7. September 2012. doi:10.1002/ajmg.a.35533. PMID 22887355. 
• "SURF-1 gene mutation associated with leukoencephalopathy in a 2-year-old". Journal of Child Neurology 24 (10): 1296–301. October 2009. doi:10.1177/0883073809333543. PMID 19805825. 
• "Maternal segmental disomy in Leigh syndrome with cytochrome c oxidase deficiency caused by homozygous SURF1 mutation". Neuropediatrics 37 (2): 88–94. April 2006. doi:10.1055/s-2006-924227. PMID 16773507. 
• "Facial dysmorphism in Leigh syndrome with SURF-1 mutation and COX deficiency". Pediatric Neurology 34 (6): 486–9. June 2006. doi:10.1016/j.pediatrneurol.2005.10.020. PMID 16765830. 
• "The first patient diagnosed with cytochrome c oxidase deficient Leigh syndrome: progress report". Journal of Inherited Metabolic Disease 29 (1): 212–3. February 2006. doi:10.1007/s10545-006-0185-3. PMID 16601896. 
• "A novel mutation in the SURF1 gene in a child with Leigh disease, peripheral neuropathy, and cytochrome-c oxidase deficiency". Journal of Child Neurology 17 (3): 233–6. March 2002. doi:10.1177/088307380201700318. PMID 12026244. 
• "A novel mutation in SURF1 causes skipping of exon 8 in a patient with cytochrome c oxidase-deficient leigh syndrome and hypertrichosis". Molecular Genetics and Metabolism 73 (4): 340–3. August 2001. doi:10.1006/mgme.2001.3206. PMID 11509016. 
• "A SURF1 gene mutation presenting as isolated leukodystrophy". Annals of Neurology 49 (6): 797–800. June 2001. doi:10.1002/ana.1060. PMID 11409433. 
• "Mutations in SURF1 are not specifically associated with Leigh syndrome". Journal of Medical Genetics 38 (2): 109–13. February 2001. doi:10.1136/jmg.38.2.109. PMID 11288709. 
• "A novel SURF1 mutation results in Leigh syndrome with peripheral neuropathy caused by cytochrome c oxidase deficiency". Neuromuscular Disorders 10 (6): 450–3. August 2000. doi:10.1016/s0960-8966(99)00122-4. PMID 10899453. 

This article incorporates text from the United States National Library of Medicine, which is in the public domain.