XKR7

Key takeaways

XKR7 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect XKR7 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of XKR7 from memory before moving on to harder problems.

Reference excerpt

XK Related 7 (XKR7) is a protein predicted to be a transmembrane protein in Homo sapiens encoded by the XKR7 gene. The primary alias is c20orf159, but it is commonly referred to as XKR7. It is predicted to be involved in apoptotic process during development.

Gene The XKR7 gene is located on plus end strand of chromosome 20 at locus 20q.11.21 and spans from 31968151 to 32003387. It is 1740 base pairs long and contains 3 exons with no known isoforms.

Gene neighbors Several other genes are near the XKR7 gene along chromosome 20. Some of the closest ones are PDRG1, TTLL9, and CCM2L.

Gene level regulation XKR7 is expressed in the brain and pancreas, but lowly at around fifteen percent. The multiple sequence alignment of XKR7 and it's orthologs showed high conservation of the 5' untranslated region where transcription factor ZNF460 binds too.

Protein The XKR7 protein contains 579 amino acids with a molecular weight of 63 kDa, and consists of 3 disordered regions, alongside 6 transmembrane regions. XKR7 was found to have high amounts of these amino acids: Leu,Val, Ile, Phe, and Met; all of which contribute to transmembrane helices. There are no major charge clusters, showing no strong cytoplasmic regulatory domains. However, the isoelectric point is 9.2, so at lower pHs, XKR7 will be positively charged.

Structure

The tertiary structure of XKR7 mostly consists of alpha helices. The most confident parts of the structure is the transmembrane region, which is highly hydrophobic and uncharged. The disordered regions are shown by red and blue, which consists of cations and anions, and is hydrophilic.

Protein level regulation There are around 7 phosphorylation sites between 2nd and 3rd transmembrane protein. Analysis on the mouse ortholog produces the exact same image with these phosphorylation sites conserved: S154, G167, T183, Y201, S206, S240, and S249. Y201 is the most functionally important site. When Y201 is phosphorylated, it’s a binding site for SH2-domain proteins (docking site), and when it’s unphosphorylated it functions as a tyrosine-based sorting signal for adaptor proteins.

Protein - protein interactions

CCM2L and PGBD5 have the highest interaction scores. Using co-IP or pull-down assays could test physical binding. Using fluorescence microscopy would verify whether the proteins are in the same cellular compartment.

Single nucleotide polymorphisms Most of the SNPs were found towards the C-term, transmembrane regions, or disordered regions.

Homology

XKR7 in Homo Sapiens has many paralogs as it’s a part of a very large X-Kell related protein family. The XKR protein family primarily functions as lipid scramblases, a crucial protein to signal for apoptosis. There are a total of seven paralogs with the two most similar to XKR7 are XKR4 and XKR6 (Ref. Paralog table). Paralogs were found using Genecards and NCBI Protein database, while the sequence similarity and identity were done through Emboss Needle.

Orthologs of XKR7 Homo sapiens are sorted by median date of divergence and then by sequence identity to XKR7 Homo sapiens. There were an overwhelming number of mammal, avian, and reptilian orthologs, but the number of orthologs decreased as the median date of divergence increased. Actinopterygii and Chondrichthyes both only had a handful of orthologs for XKR7 Homo sapiens, but it mostly consisted of orthologs for XKR7 Homo sapiens paralogs. Sequences, identity, and similarity were found using NCBI Protein and Emboss Needle.Cyclostomata, Jawless fish, are the most distantly related species to humans with the Sea Lamprey having a median date of divergent of 563 million years ago and 53% identity. Marsupials, Avians, Reptilia, with average sequence identity of 73.6% sequence identity.

Clinical significance It is suggested, using mouse shotgun data alongside humans, could hold the key to understanding diseases like Creutzfeldt-Jakob disease, a rare and fatal neurodegenerative disease from an accumulation of prions, and severe immunodeficiency. A study by Zhang et al. (2020) used RNA-seq for comparative expression in small cell lung cancer (SCLC) and adjacent normal tissue, which identified DRD2 and XKR7 upregulating SCLC. Such a significant difference suggests that XKR7 could be linked to greater tumor aggressiveness. Gnathodiaphyseal Dysplasia is also associated with XKR7, but it's not the main cause.

References

Illustrations

Worked examples

Example 1 — a first encounter with XKR7

Start with the simplest possible case. Write down what XKR7 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to XKR7 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about XKR7 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of XKR7

In research: XKR7 appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses XKR7 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: XKR7 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Genes on human chromosome 20, Proteins, so understanding it makes those chapters shorter.
In everyday life: Look for XKR7 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study XKR7 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what XKR7 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain XKR7 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is XKR7 in simple terms?

XK Related 7 (XKR7) is a protein predicted to be a transmembrane protein in Homo sapiens encoded by the XKR7 gene. The primary alias is c20orf159, but it is commonly referred to as XKR7.

Why does XKR7 matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study XKR7?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on XKR7.