Recent work on the MACPF/CDC superfamily of pore-forming proteins has focused on the structural analysis of monomers and pore-forming oligomeric complexes. We set the family of proteins in context and highlight aspects of their function which the direct and exclusive equation of oligomers with pores fails to explain. Starting with a description of the distribution of MACPF/CDC proteins across the domains of life, we proceed to show how their evolutionary relationships can be understood on the basis of their structural homology and re-evaluate models for pore formation by perforin, in particular. We furthermore highlight data showing the role of incomplete oligomeric rings (arcs) in pore formation and how this can explain small pores generated by oligomers of proteins belonging to the family. We set this in the context of cell biological and biophysical data on the proteins' function and discuss how this helps in the development of an understanding of how they act in processes such as apicomplexan parasites gliding through cells and exiting from cells.
COBISS.SI-ID: 5056026
We have described the planar lipid membranes approach, which allows direct measurement of transmembrane por formation. We have described the latest achievements and how this approach can be used to study the pore forming activity of cholesterol-dependent cytolysins.
COBISS.SI-ID: 5308186
From the fungus Pleurotus ostreatus, we isolated native bi-component pore forming proteins, ostreolysin (OlyA) and pleurotolysin B (PlyB), and produced their recombinant variants, to study their lipid-binding characteristics and mechanism of pore-formation in natural and artificial lipid membranes. We showed that OlyA binds selectively to membranes rich in cholesterol and sphingomyelin, but it does not permeabilize them. The recombinant, N-terminally truncated deltaPlyB with the membrane attack complex-perforin (MACPF) domain, spontaneously oligomerized in solution, and bound weakly and unspecifically to lipid membranes but was not able to perforate them on its own. However, binding of deltaPlyB to the cholesterol and sphingomyelin-enriched membranes, and consequently, their permeabilization was dramatically promoted in the presence of OlyA. On these membranes, deltaPlyB and OlyA formed predominantly 13-meric oligomers, with outer 19.7 nm and 4.9 nm inner diameter, as imaged with electron microscopy. These oligomers representing transmembrane pores could dimerize and thus promoted aggregation of vesicles. We found that OlyA is obligatory for the deltaPlyB binding to membranes rich in cholesterol and sphingomyelin and their permeabilization. Based on the structural and functional characteristics of deltaPlyB/OlyA pores, it was shown that they are similar to MACPF proteins and bacterial cholesterol-dependent cytolysins (CDC).
COBISS.SI-ID: 26868007