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UniProtKB/Swiss-Prot P55157: Variant p.Val168Ile

Microsomal triglyceride transfer protein large subunit
Gene: MTTP
Variant information

Variant position:  168
The position of the amino-acid change on the UniProtKB canonical protein sequence.

Type of variant:  LB/B
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:  From Valine (V) to Isoleucine (I) at position 168 (V168I, p.Val168Ile).
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:  3
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

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



Sequence information

Variant position:  168
The position of the amino-acid change on the UniProtKB canonical protein sequence.

Protein sequence length:  894
The length of the canonical sequence.

Location on the sequence:   IKRGLASLFQTQLSSGTTNE  V DISGNCKVTYQAHQDKVIKI
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                         IKRGLASLFQTQLSSGTTNEVDISGNCKVTYQAHQDKVIKI

Mouse                         LKRGLASLFQMQLSSGTTNEVDISGDCKVTYQAQQDKVVKI

Rat                           LKRGLASLFQMQLTSGTTNEVDISGDCKVTYQAQQDKVVKI

Pig                           LKRGLASLFQMQLSSGTTNEVDISGDCKVTYQAHQDKVTKI

Zebrafish                     LKRGVASMLMMQLKSGKMSEADASGKCLVEYKVNKHQVIRT

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
Chain 19 – 894 Microsomal triglyceride transfer protein large subunit
Domain 28 – 659 Vitellogenin
Alternative sequence 152 – 894 Missing. In isoform 2.
Mutagenesis 169 – 169 D -> E. No loss on localization to the endoplasmic reticulum and does not reduce interaction with APOB or P4HB/PDI, does partially reduce phospholipid or triglyceride transfer activity and apolipoprotein B secretion.
Mutagenesis 187 – 187 K -> L. No loss on localization to the endoplasmic reticulum and does not reduce interaction with APOB, but inhibits interaction with P4HB/PDI, phospholipid or triglyceride transfer activity and apolipoprotein B secretion.
Mutagenesis 187 – 187 K -> R. No loss on localization to the endoplasmic reticulum, does not reduce interaction with APOB or P4HB/PDI, partially inhibits triglyceride transfer activity, does not inhibit phospholipid transfer activity and apolipoprotein B secretion.


Literature citations

Hypobetalipoproteinemia with an apparently recessive inheritance due to a 'de novo' mutation of apolipoprotein B.
Lancellotti S.; Di Leo E.; Penacchioni J.Y.; Balli F.; Viola L.; Bertolini S.; Calandra S.; Tarugi P.;
Biochim. Biophys. Acta 1688:61-67(2004)
Cited for: VARIANTS THR-128; ILE-168 AND GLN-297;

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.