Cisbio eBook - 6

Trends in Protein-Protein Interactions Research | Protein-Protein Interactions: Lessons from the Past and Current Directions

"The idea that transmembrane domains can
make highly specific interactions is something
that much of the scientific community does not
yet appreciate," says DiMaio. While the ability of
transmembrane proteins to dimerize has been
studied, and certain critical motifs that establish
these interactions have been identified, less work
has focused on the ability of different transmembrane domains to interact with one another. "Our
work has confirmed that these can be very highly
specific interactions," continues DiMaio.
In a recent study published in eLife, DiMaio and
colleagues analyzed 26-amino-acid artificial
transmembrane proteins known as traptamers,
which contain one transmembrane helix and
consist exclusively of leucine and isoleucine residues, two structurally very similar hydrophobic
amino acids. When expressed in cells, some trap6 |

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intracellular membranes. Many transmembrane
protein domains interact with each other in a
highly specific way to ensure proper protein
folding or to mediate protein oligomerization or
complex formation.

tamers activate the erythropoietin receptor, and
others activate the platelet-derived growth factor
The researchers found that changing a single
methyl group at specific positions in the traptamer changed its target specificity. "This finding
was surprising and made us wonder what a
conservative mutation is, because one cannot

be more conservative than a leucine to isoleucine change, yet this very small chemical change
had a very profound effect on activity," explains
The focus on these transmembrane protein
domains in DiMaio's group began with their
finding that bovine papillomavirus E5, a
short transmembrane protein, turns on the

Cisbio eBook

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