Frataxin is a protein capable of storing, releasing and detoxifying intracellular iron. A mutation in this protein can trigger the Friedreich's ataxia, a neurodegenerative disease caused due to incapacity to form iron-sulfur groups necessary to activating the mitochondrial enzyme involved in the electron transportation chain, aconitase.
It is presented as a polymeric molecule that is composed of several subunits of a trimer of organized units, which exhibit several interactions between one another to maintain the structure of the trimer, (?) for example the interactions of the N-terminal chains with the interacions of the N-terminals between each other bases, forming not only the core of the trimer, but the canal as well.
In the box at the right, it is possible to see its in a space-fill model, in which violet, orange and light-green represents, each, a different monomer of the entire molecule.
However, to cover some important aspects of the structure and function of the molecule, it is particularly useful to represent its .
The trimeric structure of frataxin is stabilized by the of each subunit, shown in yellow. Viewing of the molecule, we can notice how the N-terminal extensions, still in yellow, interact with the adjacent monomer. Taking a , we figure out how the N-terminal loop of the first monomer, here described as chain A, is placed with respect to chain B.
But how exactly is this process possible? If we the details, we see some residues close enough to interact. Those are their specified by their positions.
Let's now (...) We can the residues differently according to their hydrophilicity. Polar residues are represented in pink, while the hydrophobic ones appear gray. Now we are about to all those relevant residues to specify their interactions. The can be seen. Here, Pro 62, Val 65 and Leu 68, shown in dark-blue, are packed against the polar uncharged aminoacids Thr 110 and Thr 118, in red (other aminoacids ar shown in turquoise). This interaction among the hydrophobic residues contributes to the maneintance of the loop configuration of the N-terminal region at its extremity. Another important interaction is the formed between Glu 64 and Thr 118. Those are the only residues able to form hydrogen bond, since the is within a range of . Pay special attention it the role of the carbonyl oxygen of Glu 64 involved in the hydrogen bonding.
Now, we can devote our attention to examine what occurs at the .Those are the in relevant interactions that contribute to the stabilization of the trimeric form. Those are their specific . If we color according to their polarities, we realize that (CONTINUAR)? So, no hydrophobic packing here. Instead, we have hydrogen bonds as the main eletrostatic interaction. Notice the elements composing each aminoacid: in this color scheme, carbons are greygrey, oxygens are red and nitrogens are blueblue (C,O, N).
The hydrogen bonds are essentialy formed between , , , , and
If we color the residues according to their ,
If we take a closer look to the
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