Correlations between differences in amino-terminal sequences and different hemolytic activity of sticholysins

The membranotropic activity of N-terminal peptides from the pore-forming proteins sticholysin I and II is modulated by hydrophobic and electrostatic interactions as well as lipid composition

“…St II peptide is cationic at pH 7 (net charge +2) in contrast to StI 1-31 , which has no net charge. In a previous characterization of peptide activity, we demonstrated that StII 1-30 is 3-fold more active than StI 1-31 , qualitatively reproducing the differential hemolytic activity of toxins, which suggests that the N-terminal plays a key role in protein function (Cilli et al 2007).…”

“…In addition we studied binding of StI 1-31 and StII 1-30 to more complex monolayers of PC:SM:PA:Chol in an attempt to approach the lipid heterogeneity of erythrocyte membrane, a classical model target for studying the actinoporins' activity and their peptides (Cilli et al 2007). It is remarkable that both peptides attain π c values higher than 35 mN m −1 (figure 2 A and B), indicating that they probably penetrate this lipid monolayer (Caaveiro et al 2001).…”

Biophysical and biochemical strategies to understand membrane binding and pore formation by sticholysins, pore-forming proteins from a sea anemone

“…The fact they are active, albeit in a higher concentration range than the full-length proteins, reinforces the notion that these small molecules can mimic the functional behavior of actinoporins. Of relevance, the hemolytic and permeabilizing activity of the peptides reproduced qualitatively the behavior of their respective parental proteins (Cilli et al 2007;Ros et al 2011Ros et al , 2013, an observation that we could even extend to the other members of the actinoporins family EqtII and FraC . This study of the four most studied actinoporins strongly suggest the importance of continuity of the 1-10 hydrophobic amino acid sequence in StII1-30 for displaying higher membrane binding and activity.…”

“…However, in the presence of membrane mimetic systems they adopted an α-helical structure, similar to that adopted by these segments in the fullprotein structure, which supports their suitability as models of the N-terminus structure of Sts. Biologically relevant peptides are active against human red blood cells (Casallanovo et al 2006;Cilli et al 2007) and liposomes (Ros et al 2011(Ros et al , 2013 in a micromolar concentration range, despite their small size and the absence of the Sts binding site to the membrane (Casallanovo et al 2006;Cilli et al 2007;Ros et al 2011Ros et al , 2013. The fact they are active, albeit in a higher concentration range than the full-length proteins, reinforces the notion that these small molecules can mimic the functional behavior of actinoporins.…”

“…This approach has been useful to gain an understanding of the influence of the N-terminus on folding and activity of Sts. To clarify the contribution of the first 30 (StII) or 31 (StI) N-terminal amino acid residues to the activity of the toxins, four peptides spanning residues 1-31 of StI (StI1-31, StI12-31) and residues 1-30 of StII (StII1-30, StII11-30) were synthesized and their structural and functional properties investigated (Casallanovo et al 2006;Cilli et al 2007;Ros et al 2011Ros et al , 2013. The peptides were characterized by a high structural plasticity; however, in solution, most of them were largely unordered, which was not unexpected as peptides that are not constrained by disulfide bonds are often very flexible and do not adopt regular secondary structures in aqueous solution.…”