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UniProtKB/Swiss-Prot Q99250: Variant p.Met136Ile

Sodium channel protein type 2 subunit alpha
Gene: SCN2A
Variant information

Variant position:  136
The position of the amino-acid change on the UniProtKB canonical protein sequence.

Type of variant:  Disease [Disclaimer]
The variants are classified into three categories: Disease, Polymorphism and Unclassified.
  • Disease: Variants implicated in disease according to literature reports.
  • Polymorphism: Variants not reported to be implicated in disease.
  • Unclassified: Variants with uncertain implication in disease according to literature reports. Evidence against or in favor of a pathogenic role is limited and/or conflicting.

Residue change:  From Methionine (M) to Isoleucine (I) at position 136 (M136I, p.Met136Ile).
Indicates the amino acid change of the variant. The one-letter and three-letter codes for amino acids used in UniProtKB/Swiss-Prot are those adopted by the commission on Biochemical Nomenclature of the IUPAC-IUB.

Physico-chemical properties:  Similar physico-chemical property. Both residues are medium size and hydrophobic.
The physico-chemical property of the reference and variant residues and the change implicated.

BLOSUM score:  1
The score within a Blosum matrix for the corresponding wild-type to variant amino acid change. The log-odds score measures the logarithm for the ratio of the likelihood of two amino acids appearing by chance. The Blosum62 substitution matrix is used. This substitution matrix contains scores for all possible exchanges of one amino acid with another:
  • Lowest score: -4 (low probability of substitution).
  • Highest score: 11 (high probability of substitution).
More information can be found on the following page

Involvement in disease:  Epileptic encephalopathy, early infantile, 11 (EIEE11) [MIM:613721]: An autosomal dominant seizure disorder characterized by neonatal or infantile onset of refractory seizures with resultant delayed neurologic development and persistent neurologic abnormalities. Patients may progress to West syndrome, which is characterized by tonic spasms with clustering, arrest of psychomotor development, and hypsarrhythmia on EEG. {ECO:0000269|PubMed:19783390, ECO:0000269|PubMed:19786696, ECO:0000269|PubMed:20956790, ECO:0000269|PubMed:22677033, ECO:0000269|PubMed:23033978, ECO:0000269|PubMed:23195492, ECO:0000269|PubMed:23550958, ECO:0000269|PubMed:23662938, ECO:0000269|PubMed:23708187, ECO:0000269|PubMed:23935176, ECO:0000269|PubMed:23988467, ECO:0000269|PubMed:24463883, ECO:0000269|PubMed:24579881, ECO:0000269|PubMed:24659627, ECO:0000269|PubMed:24710820, ECO:0000269|PubMed:25457084, ECO:0000269|PubMed:25459969, ECO:0000269|PubMed:25772804, ECO:0000269|PubMed:25818041, ECO:0000269|PubMed:26138355, ECO:0000269|PubMed:26291284, ECO:0000269|PubMed:26993267, ECO:0000269|PubMed:27864847, ECO:0000269|PubMed:29625812, ECO:0000269|PubMed:29844171, ECO:0000269|PubMed:30144217, ECO:0000269|PubMed:30415926}. Note=The disease is caused by mutations affecting the gene represented in this entry.
The name and a short description of the disease associated with the variant. For more information about the disease, the user can refer to OMIM, following the link provided after the disease acronym.

Variant description:  In EIEE11; responds to ketogenic diet.
Any additional useful information about the variant.

Sequence information

Variant position:  136
The position of the amino-acid change on the UniProtKB canonical protein sequence.

Protein sequence length:  2005
The length of the canonical sequence.

The residue change on the sequence. Unless the variant is located at the beginning or at the end of the protein sequence, both residues upstream (20) and downstream (20) of the variant will be shown.

Residue conservation: 
The multiple alignment of the region surrounding the variant against various orthologous sequences.




Sequence annotation in neighborhood:  
The regions or sites of interest surrounding the variant. In general the features listed are posttranslational modifications, binding sites, enzyme active sites, local secondary structure or other characteristics reported in the cited references. The "Sequence annotation in neighborhood" lines have a fixed format:
  • Type: the type of sequence feature.
  • Positions: endpoints of the sequence feature.
  • Description: contains additional information about the feature.

Chain 1 – 2005 Sodium channel protein type 2 subunit alpha
Transmembrane 130 – 148 Helical; Name=S1 of repeat I
Repeat 111 – 456 I
Helix 129 – 145

Literature citations

Targeted resequencing in epileptic encephalopathies identifies de novo mutations in CHD2 and SYNGAP1.
Carvill G.L.; Heavin S.B.; Yendle S.C.; McMahon J.M.; O'Roak B.J.; Cook J.; Khan A.; Dorschner M.O.; Weaver M.; Calvert S.; Malone S.; Wallace G.; Stanley T.; Bye A.M.; Bleasel A.; Howell K.B.; Kivity S.; Mackay M.T.; Rodriguez-Casero V.; Webster R.; Korczyn A.; Afawi Z.; Zelnick N.; Lerman-Sagie T.; Lev D.; Moeller R.S.; Gill D.; Andrade D.M.; Freeman J.L.; Sadleir L.G.; Shendure J.; Berkovic S.F.; Scheffer I.E.; Mefford H.C.;
Nat. Genet. 45:825-830(2013)
Cited for: VARIANTS EIEE11 ILE-136; ASN-905; CYS-928 AND GLN-1882;

SCN2A encephalopathy: A major cause of epilepsy of infancy with migrating focal seizures.
Howell K.B.; McMahon J.M.; Carvill G.L.; Tambunan D.; Mackay M.T.; Rodriguez-Casero V.; Webster R.; Clark D.; Freeman J.L.; Calvert S.; Olson H.E.; Mandelstam S.; Poduri A.; Mefford H.C.; Harvey A.S.; Scheffer I.E.;
Neurology 85:958-966(2015)
Cited for: VARIANTS EIEE11 ILE-136; LYS-218; LEU-856; ASN-905; CYS-928; ARG-1593; VAL-1634 AND GLN-1882; VARIANT BFIS3 SER-240; VARIANT LYS-976;

Ketogenic diet as a successful early treatment modality for SCN2A mutation.
Turkdogan D.; Thomas G.; Demirel B.;
Brain Dev. 41:389-391(2019)
Cited for: VARIANT EIEE11 ILE-136;

Disclaimer: Any medical or genetic information present in this entry is provided for research, educational and informational purposes only. They are not in any way intended to be used as a substitute for professional medical advice, diagnostic, treatment or care.