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UniProtKB/Swiss-Prot P09848: Variant p.Gln268His

Lactase-phlorizin hydrolase
Gene: LCT
Variant information

Variant position:  268
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 Glutamine (Q) to Histidine (H) at position 268 (Q268H, p.Gln268His).
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 polar.
The physico-chemical property of the reference and variant residues and the change implicated.

BLOSUM score:  0
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:  Congenital lactase deficiency (COLACD) [MIM:223000]: Autosomal recessive, rare and severe gastrointestinal disorder. It is characterized by watery diarrhea in infants fed with breast milk or other lactose-containing formulas. An almost total lack of LCT activity is found in jejunal biopsy material of patients with congenital lactase deficiency. Opposite to congenital lactase deficiency, also known as lactose intolerance, is the most common enzyme deficiency worldwide. It is caused by developmental down-regulation of lactase activity during childhood or early adulthood. The decline of lactase activity is a normal physiological phenomenon; however, the majority of Northern Europeans have the ability to maintain lactase activity and digest lactose throughout life (lactase persistence). The down-regulation of lactase activity operates at the transcriptional level and it is associated with a noncoding variation in the MCM6 gene, located in the upstream vicinity of LCT. {ECO:0000269|PubMed:16400612}. 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 COLACD.
Any additional useful information about the variant.

Other resources:  
Links to websites of interest for the variant.



Sequence information

Variant position:  268
The position of the amino-acid change on the UniProtKB canonical protein sequence.

Protein sequence length:  1927
The length of the canonical sequence.

Location on the sequence:   LDLSYECQNEASLRQKLSKL  Q TIEPKVKVFIFNLKLPDCPS
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.

Human                         LDLSYECQNEASLRQKLSKLQTIEPKVKVFIFNLKLPDCPS

Rat                           LDLSYECQSVATLPQKLSELQNLEPKVKVFIYTLKLEDCPA

Rabbit                        LDLSYECQSEMSLPEKLSKLQTIEPKVKVFIFTLRLQDCPS

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.

TypePositionsDescription
Propeptide 20 – 868 Beta-glucosidase
Topological domain 20 – 1882 Extracellular
Region 87 – 1841 4 X approximate repeats


Literature citations

Mutations in the translated region of the lactase gene (LCT) underlie congenital lactase deficiency.
Kuokkanen M.; Kokkonen J.; Enattah N.S.; Ylisaukko-Oja T.; Komu H.; Varilo T.; Peltonen L.; Savilahti E.; Jaervelae I.;
Am. J. Hum. Genet. 78:339-344(2006)
Cited for: VARIANTS COLACD HIS-268 AND SER-1363;

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.