The micro-exon genes (MEG) of Schistosoma mansoni, a parasite responsible for the second most widely spread tropical disease, code for small secreted
proteins with sequences unique to the Schistosoma genera. Bioinformatics analyses suggest the soluble domain of the MEG-14
protein will be largely disordered, and using
synchrotron radiation circular dichroism spectroscopy, its secondary structure was shown to be essentially completely unfolded in aqueous
solution. It does, however, show a strong propensity to fold into more ordered structures under a wide range of conditions. Partial folding was produced by increasing temperature (in a reversible process), contrary to the behavior of most soluble
proteins. Furthermore, significant folding was observed in the presence of negatively charged
lipids and
detergents, but not in zwitterionic or neutral
lipids or
detergents. Absorption onto a surface followed by
dehydration stimulated it to fold into a helical structure, as it did when the aqueous
solution was replaced by nonaqueous
solvents. Hydration of the dehydrated folded
protein was accompanied by complete unfolding. These results support the identification of MEG-14 as a classic
intrinsically disordered protein, and open the possibility of its interaction/folding with different partners and factors being related to multifunctional roles and states within the host.