MIT biologists have conducted in-depth studies of repetitive protein sequences

About 70% of human proteins contain at least one sequence consisting of a single amino acid that is repeated many times, interspersed with some other amino acids

The proteins that contain these sequences have many different functions, but MIT biologists have now come up with a way to identify and study

Using their technique, the researchers analyzed all the proteins

Byron Lee, a graduate student at MIT, said: "We didn't study specific LCRs and their functions because they are involved in different processes, so they appear to be separate, and our broader approach allows us to see similarities between their properties, suggesting that the function of

The researchers also found some differences between LCR sequences of different species and showed that these species-specific LCR sequences correspond to species-specific functions, such as forming plant cell walls

Lee and graduate student Nima Jaberi-Lashkari are lead authors of the study, published today in eLife

Large-scale research

Previous studies have shown that LCRs are involved in a variety of cellular processes, including cell adhesion and DNA binding

Finding these sequences and then studying their function one by one was a time-consuming process, so the MIT team decided to use bioinformatics — a method that uses computational methods to analyze large amounts of biological data — to evaluate

"What we want to do is take a step back, instead of looking at individual LCRs, but try to look at all LCRs and see if we can observe some patterns on a larger scale, which may help us figure out what LCRs that have specified features are doing, and also help us understand what some LCRRs that don't have specified features are doing

To do this, the researchers used a technique called dot matrix, a method of visually representing amino acid sequences that can generate images

Using this technique, the researchers were able to classify

As a demonstration, the researchers picked out a human protein called RPA43, which has three lysine-rich LCRs

Biological components

In comparing proteins found in 8 different species, the researchers found that some LCR types are highly conserved between species, meaning that sequences change little on evolutionary timescales

"These sequences seem to be important for the assembly of certain parts of the nucleoli," Lee said

The researchers also found differences

Another structure that appears to have many conserved LCRs is the nucleus plaque, which is found

The team also found some examples of structures with LCRs that appear to diverge
between species.
For example, plants have unique LCR sequences in the proteins they use to support cell walls, which are not seen in other types of organisms
.

The researchers now plan to extend their LCR analysis to other species
.

"There's a lot to explore because we can extend this map to any species," Lee said
.
"This gives us the opportunity and framework to identify new combinations of organisms
.
"

essay

A unified view of low complexity regions (LCRs) across species