Transmembrane protein 155 is a protein that in humans is encoded by the TMEM155gene. It is located on human chromosome 4, spanning 6,497 bases.[3] It is also referred to as FLJ30834 and LOC132332.[4] This protein is known to be expressed mainly in the brain, placenta, and lymph nodes and is conserved throughout most placental mammals.[5] The function and structure of this protein is still not well understood, but its level of expression has been studied pertaining to various pathologies.
Gene
Locus
TMEM155 is located on the minus strand of human chromosome 4 (4q27) and spans 13,611 base pairs.[6]
TMEM155 is neighbored by TMEM155 is neighbored on chromosome 4 by CCNA2, a gene encoding for cyclin A2, and ANXA5, which encodes annexin A5.[4] It is also neighbored by PP12613 located on the positive strand.
Size
The gene on chromosome 4 encoding for TMEM155 spans 6,487 nucleotides.[5] This gene spans from base pairs 121,758,930 and 121,765,427 on chromosome 4.[3] The longest variant ofTMEM155 has 5 exons detailed in the table below:[5]
Exon #
Base pairs
Length (bp)
1
1-348
348
2
349-457
108
3
458-529
71
4
530-884
354
5
885-2429
1544
mRNA
Isoforms
There are 7 isoforms of TMEM155 precursor mRNA.[5] TMEM155 isoform 5 is the longest mRNA and is 2,429 bp long.[3] The shortest isoform is variant 4 and this variant is 2,035 bp long.[5] Isoforms are detailed in the table below.[5]
Isoform Number
Length (bp)
Exons
Isoform 1
2,295
6
Isoform 2
2,160
6
Isoform 3
2,157
6
Isoform 4
2,035
6
Isoform 5
2,429
5
Isoform 6
2,294
5
Isoform 7
2,292
6
Protein
Primary Structure
TMEM155 protein is 130 amino acids in length.[3] The TMEM155 protein in its full form is 14.2 kD in molecular weight with an isoelectric point of 10.29[7] Without its signal peptide it is 11.8 kD.[7] The protein interacts with the membrane once, with one transmembrane domain as seen below.
TMEM155 has a single transmembrane domain through the membrane of the ER.[8]
The tertiary structure of TMEM155 is predicted in the image on the right. This is predicted to be the structure of the N-terminus tail of TMEM155 located inside the ER membrane.
There are several promoters of the TMEM155 gene.[17] The promoter region of the gene is bound by several transcription factors involved in regulating chromatin structure, development, cell cycle, and immune responses.[18] TMEM155 is expressed highly in the brain, placenta, and lymph nodes.[5] Below is a table detailing the transcription factor binding sites for the GXP_319937 promoter of TMEM155.[18] The table below details the transcription factors that bind the promoter region of TMEM155 and the sequences which they bind.
Divergence rate of TMEM155 compared to known fast diverging gene, fibrinogen, and slowly diverging gene, CytC. This graph shows the percent change in amino acid sequence over the date of divergence of the sequence from humans.
TMEM155 is evolving at the molecular level rather quickly. When compared to fibrinogen protein rate of evolution, the TMEM155 appears to be accumulating more amino acid changes in a shorter amount of time. Because it is faster than the quickly evolving fibrinogen, it is also evolving faster than cytochrome C protein, which is known to evolve slowly.
Homology
TMEM155 is conserved across most placental mammals.[5] DoD (MYA) refers to how many million years ago the gene diverged from the human version of the gene.[20]
TMEM155 regulation co-varies with families that have instances of essential tremor,[23]
Female reproductive tissues
Hypermethylated TMEM155 is a potential biomarker for HER2+ breast cancer.[24] The expression of TMEM155 was found to be higher in the oocytes of women with low antral follicular count, meaning it could be involved in the regulation of female fertility.[25]
^Renaud B, Buda M, Lewis BD, Pujol JF (September 1975). "Effects of 5,6-dihydroxytryptamine on tyrosine-hydroxylase activity in central catecholaminergic neurons of the rat". Biochemical Pharmacology. 24 (18): 1739–42. doi:10.1016/0006-2952(75)90018-0. PMID17.
