Bridge-like lipid transfer protein family member 1 BLTP1 (previously known as KIAA1109) is a protein that in humans is encoded by the BLTP1gene. This protein functions as a molecular bridge involved in the transport of lipids from the endoplasmic reticulum to phospholipid membranes.
Other aliases included FSA (fragile site-associated) protein, MGC110967 and DKFZp781P0474.
An ortholog of BLTP1 has been found in Drosophila, responsible for regulating synaptic vesicle recycling and certain brain related functions. Drosophila exhibiting mutated BLTP1 were unable to walk or stand upright for long periods and exhibited seizures, reminiscent of severe neurological defects. This led to it being given the name "Tweek", after a character in South Park.
Gene
Location
BLTP1 is found on the long arm of chromosome 4 (4q27), with the genomic sequence starting at 118,818,167 bp and ending at 119,010,362 bp
Gene neighborhood
The gene neighborhood of BLTP1 involves 4 other genes. BLTP1 is a part of the BLTP1/Tenr/IL2/IL21 gene region. This region consists of the three genes to the right of BLTP1; ADAD1, IL2 and IL21.
Another gene located in the neighborhood of BLTP1 is TRPC3. This gene is to the left of BLTP1 on the opposite side of the genes described above.
Expression
According to data on NCBI's EST Abundance Profile page for BLTP1, the gene is expressed in many different tissues in humans. Human expression is seen most predominately in parathyroid, muscle, ear, eye, mammary gland, lymph node, thymus in addition to 27 other tissues. BLTP1 is also expressed in various disease states including 12 different tumors as well as bladder carcinoma, chondrosarcoma, glioma, leukemia, lymphoma, non-neoplasia, retinoblastoma tissues. BLTP1 is expressed in all stages of development from embryoid body to adult, except in infants. No expression of my gene is seen during the infant stage of development.
Promoter
According to Genomatix's ElDorado program the promoter region of BLTP1 is predicted to be 601 base pairs in length. The promoter region starts 500 base pairs upstream of the 5' UTR of BLTP1 mRNA transcript and contains part of this 5' UTR.
Homology
BLTP1 is conserved throughout many species. Orthologs have been found in many mammals and other vertebrates. More distant homologs have been identified in animals such as insects. See the mRNA and protein conservation sections below for more details. No human paralogs for BLTP1 have been identified.
mRNA
Splice variants
BLTP1 has 13 mRNA splice variants and 6 unspliced variants. Variant A is the longest and most commonly occurring variant of the gene and is the subject of this article. BLTP1 variant A is made up of 84 exons and is 15,592 base pairs in length. The accession number for this nucleotide is NM_015312.3.
Conservation
The mRNA sequence of BLTP1 is highly conserved throughout mammals. The mRNA sequence identity to mammals is no less than 81.9% (in platypus) and ranging up to 99.5% (in chimpanzees). Birds also show fairly high conservation with mRNA sequence identities around 78% in zebra finches.
The table blow shows information on the mRNA orthologs.
BLTP1 protein is 5005 amino acids in length, and has a predicted molecular weight of 555519.38 daltons. The isoelectirc point of BLTP1 protein is predicted to be 6.12.
Composition
The amino acid composition of BLTP1 protein showed amino acid frequencies within 1.5% of that of normal human proteins for all but Alanine, Serine and Threonine. Alanine has a lower frequency in BLTP1 than in that of a normal human protein while Serine and Threonine both have a higher frequency in BLTP1 than in the average human protein.
Conservation
The amino acid sequence of BLTP1 is highly conserved throughout mammals. The protein identity ranges from 93.2% in Opossum to 99.8% in Chimpanzees and protein similarity is no less than 97% in all mammals included. Birds continue to show fairly high conservation with protein identities around 90% and proteins similarities at a high 96%. While conservation is still high the lower numbers may be due to small truncations on either, the 5' and 3' ends of these sequences.
As we move to the more distant species of zebra fish and then the red four beetle and carpenter ant the conservations drops. In the insects the protein identities are down to around 34%.
Genus and species name
Common name
Protein accession number
Sequence length (amino acids)
Sequence identity to human protein
Sequence similarity to human protein
Homo sapiens
Human
NP_056127.2
5005
Pan troglodytes
Chimpanzee
XP_517422.2
5005
99.8%
99.8%
Macaca mulatta
Rhesus macaque
XP_001102884.1
5007
99.2%
99%
Callithris jacchus
Marmoset
XP_002745479.1
5004
98.9%
99%
Equus caballus
Horse
XP_001916017.1
5006
98%
99%
Ailuropoda melanoleuca
Giant panda
XP_002923867.1
5005
98.1%
99%
Oryctolagus cuniculus
Rabbit
XP_002717281.1
5004
97.8%
99%
Mus musculus
Mouse
NP_766267.2
5005
96.7%
99%
Canis familiaris
Dog
XP_540963.2
4944
96.4%
99%
Monodelphis domestica
Opossum
XP_001370606.1
5015
93.2%
97%
Ornithorhynchus anatinus
Platypus
XP_001513983.1
5012
93.3%
97%
Taeniopygia guttata
Zebra finch
XP_002188285.1
4999
90.7%
96%
Gallus gallus
Chicken
XP_420625.2
5040
89.9%
96%
Danio rerio
Zebra fish
NP_001139056.1
4922
74.2%
84%
Tribolium castaneum
Red flour beetle
XP_972174.2
4598
34.8%
49%
Camponotus floridanus
Carpenter ant
EFN75044.1
4979
34.3
Conserved domains
NCBI conserved domains search identified two domains in BLTP1. The first is the fragile site associated C-terminus, which is said to be linked to celiac disease susceptibility according to genome-wide-association studies and may also be associated with polycystic kidney disease. The second conserved region identified by NCBI in BLTP1 is an uncharacterized conserved protein (DUF2246), whose function is unknown and is conserved in various species from humans to worms.
Post translation modifications
BLTP1 is predicted to undergo various types of post translational modifications including glycate, N-glycosylation, O-GlcNAc, O Glycosylation, Sulfonation and Phosphorylation.
Subcellular localization
BLTP1 contains one transmembrane domain from amino acids 26–46.
No signal peptides, mitochondrial targeting sequences or chloroplast peptides were predicted for my protein and it is therefore not predicted to localize to secretory pathway, mitochondria or chloroplast.
Interacting proteins
MADH2 and Beta-catenin were both found to have a physical interaction with my protein as detached by display technonloy by Miyamoto-Sato et al. 2010.
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