About ANKR / Ankyrin Repeat Domain:
ANKR, or ankyrin repeat, is a collection of proteins that repeats in the genome. It consists of two alpha helices that are separated by loops similar to those in yeast Cdc10 and Drosophila Notch. Ankyrin repeat domains consist of ankyrin tandem repeats are the most common structural motifs in the body as well as in other living organisms. From the proteins of small bacterial, archaeal, and eukaryotic organisms to humans - they are prolific in the living world. They are most commonly seen in eukaryotes. Ankyrin repeat domains are common also in poxviruses, however they do not show up in most viruses.
ANKR usually shows up in repeats of four or six, and this is common in many proteins. However ankyrin itself, which is the namesake of this repeat structure, contains 24 repeats of this kind. The largest number of repeats that has been recorded is present in the organism giardia lamblia and consists of 34 repeats.
Ankyrin Repeat Domain Mechanism
Usually when Ankyrin repeats are present inside the structure of a protein they will fold together and form a solenoid structure called ankyrin repeat domains. These domains are one of the most popular protein interaction platforms we see in nature. They occur in a wide array of proteins all over the living world including those of eukaryotes.
The reason why there are few of these interactions present in viruses or prokaryotes is likely due to their horizontal gene transfers which differ from the vertical gene transfers seen in most reproductive systems.
Ankyrin Repeat Domain Function
The repeat has been found in proteins that have a lot of different functions such as cell cycle regulators, signal transductors, and even ion transporters. It is important to note that the ankyrin repeat domain is defined by its structure and not the function it performs in the body. The reason for this is that there is no specific function it seems to perform.