Disorder and amino acid composition in proteins: their potential role in the adaptation of extracellular pilins to the acidic media, where Acidithiobacillus thiooxidans grows

Understanding a Core Pilin of the Type IVa Pili of Acidithiobacillus thiooxidans, PilV

“…Remarkable, during denaturation with urea, there is an increase in fluorescence intensity, a phenomenon that has already been observed in other proteins, most likely due to the removal of other tryptophan quenching as the protein unfolds [ 50 ]. Finally, it is important to say that PilV has 2 tryptophan residues in its sequence [ 32 ].…”

“…3C '). Disorder analysis shows that the entire αβ-loop region is located precisely at the peak of the most disordered region of PilV of A. thiooxidans , but it could transition into an ordered state [ 32 ]. Additionally, it has been observed that the αβ-loop is involved in the proper assembly of pilins and exhibits a slow structural dynamic (μs to ms) [ 57 ], suggesting its role in protein-protein interactions.…”

“…Previously we reported that the pili of A. thiooxidans exhibit characteristics that would make them resilient to changes in pH and reducing environments [ 32 ]. Here, specifically for the PilV pilin, we evaluated specific regions of the tertiary structure that are known to be in contact with the external environment.…”

“…PilV of A. thiooxidans shares up to 93% homology with PilV of A. ferrooxidans in its mature form [ 20 ]. Recently we found that PilV is in a cluster fimT-pilW-pilV-pilX-pilY1 similar to the minor-pilins cluster of P. aeruginosa [ 32 ]. It is clear that pathogenic and acidophilic bacteria have type IV pili (T4P); therefore, their pili are in contact with different external environments.…”

“…On the other hand, bacterial T4P also exhibit features that suggest acid stability, characterized by a composition rich in polar amino acids and a low proportion of charged amino acids, as discussed in a recent study by Páez-Pérez et al . [ 32 ]. Similar trends in amino acid composition have been observed in pili-like structures in A. ferrooxidans , most likely reflecting a responsive variation linked to the protein stabilization at low pH [ 37 ].…”