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UniProtKB/Swiss-Prot variant pages

UniProtKB/Swiss-Prot P08397: Variant p.His256Tyr

Porphobilinogen deaminase
Gene: HMBS
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Variant information Variant position: help 256 The position of the amino-acid change on the UniProtKB canonical protein sequence.
Type of variant: help LP/P [Disclaimer] The variants are classified into three categories: LP/P, LB/B and US.
  • LP/P: likely pathogenic or pathogenic.
  • LB/B: likely benign or benign.
  • US: uncertain significance
Residue change: help From Histidine (H) to Tyrosine (Y) at position 256 (H256Y, p.His256Tyr). 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: help Change from medium size and polar (H) to large size and aromatic (Y) The physico-chemical property of the reference and variant residues and the change implicated.
BLOSUM score: help 2 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
Variant description: help In AIP; severely decreased hydroxymethylbilane synthase activity. Any additional useful information about the variant.


Sequence information Variant position: help 256 The position of the amino-acid change on the UniProtKB canonical protein sequence.
Protein sequence length: help 361 The length of the canonical sequence.
Location on the sequence: help GVLHDPETLLRCIAERAFLR H LEGGCSVPVAVHTAMKDGQL 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: help The multiple alignment of the region surrounding the variant against various orthologous sequences. 
Human                         GVLHDPETLLRCIAERAFLRHLEGGCSVPVAVHTAMK-----DGQL

Mouse                         SVLHDPETLLRCIAERAFLRHLEGGCSVPVAVHTVMK----

Rat                           GVLHDPETLLRCIAERAFLRHLEGGCSVPVAVHTVMK----

Bovine                        GVLHDPETLLRCIAERSFLRHLEGGCSVPVAVHTAIK----

Slime mold                    NPLIHRESMYCCEAERSMLRDLEGGCHVPIGVVTKLHNQSQ

Baker's yeast                 DEICDLNATICCLSERALMRTLEGGCSVPIGVESKYN---E

Fission yeast                 KPLQHQETLYACLAERALMKRLQGGCAIPIGVQTDVLAISN
Sequence annotation in neighborhood: help 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
Chain 2 – 361 Porphobilinogen deaminase
Modified residue 261 – 261 S-(dipyrrolylmethanemethyl)cysteine
Alternative sequence 218 – 257 Missing. In isoform 3 and isoform 4.
Helix 241 – 257



Literature citations
Molecular epidemiology and diagnosis of PBG deaminase gene defects in acute intermittent porphyria.
Puy H.; Deybach J.-C.; Lamoril J.; Robreau A.-M.; Da Silva V.; Gouya L.; Grandchamp B.; Nordmann Y.;
Am. J. Hum. Genet. 60:1373-1383(1997)
Cited for: VARIANTS AIP SER-24; ASN-28; ASP-124; ASN-178; HIS-217; ALA-250; VAL-250; TYR-256; MET-267; ASP-270 AND ASP-335; Acute intermittent porphyria in Sweden. Molecular, functional and clinical consequences of some new mutations found in the porphobilinogen deaminase gene.
Floderus Y.; Shoolingin-Jordan P.M.; Harper P.;
Clin. Genet. 62:288-297(2002)
Cited for: VARIANTS AIP CYS-26; HIS-26; VAL-86; PRO-92; GLY-99; ARG-111; THR-113; GLN-173; ASN-178; GLN-225; GLY-225; TYR-256; ASP-260 AND PRO-343; From a dominant to an oligogenic model of inheritance with environmental modifiers in acute intermittent porphyria.
Lenglet H.; Schmitt C.; Grange T.; Manceau H.; Karboul N.; Bouchet-Crivat F.; Robreau A.M.; Nicolas G.; Lamoril J.; Simonin S.; Mirmiran A.; Karim Z.; Casalino E.; Deybach J.C.; Puy H.; Peoc'h K.; Gouya L.;
Hum. Mol. Genet. 27:1164-1173(2018)
Cited for: VARIANTS AIP PHE-30 AND GLU-235; CHARACTERIZATION OF VARIANTS AIP SER-24; CYS-26; HIS-26; ASN-28; PHE-30; MET-35; PHE-96; ARG-111; TRP-116; ASP-124; GLN-149; LEU-149; HIS-217; GLU-235; ARG-247; ALA-250; GLN-250; VAL-250; TYR-256 AND MET-267;
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.