Self-assembly protein folding

The particular shape of protein chains is known as a fold and the process is called chain folding. While chain folding is often referred to as a self-assembly process, it also involves other specialized separate proteins that assist in this chain folding, so it is not truly self-assembly. Chain folding occurs rapidly in the timescale of 1-10 psec. 

In reconstitution experiments, the self-assembly of the pore-forming protein a-hemolysin of Staphylococcus aureus (aHL) [181-183] was examined in plain and S-layer-supported lipid bilayers. Staphylococcal aHL formed lytic pores when added to the lipid-exposed side of the DPhPC bilayer with or without an attached S-layer from B coagulans E38/vl. The assembly of aHL pores was slower at S-layer-supported compared to unsupported folded membranes. No assembly could be detected upon adding aHL monomers to the S-layer face of the composite membrane. Therefore, the intrinsic molecular sieving properties of the S-layer lattice did not allow passage of aHL monomers through the S-layer pores to the lipid bilayer [142]. 

Self-assembly is the spontaneous organization of molecules into stable, well-defined structures with the driving forces being noncovalent associations. The final structure is normally near or at the thermodynamic equilibrium arrangement allowing it to form spontaneously. Such formations can be done under conditions where defects are either minimized or eliminated. In nature, self-assembly is common as in the folding of proteins, formation of the DNA double helix, etc. 

The simplest way in which a process occurs by itself is when it is under thermodynamic control. The folding of a protein, or the self-assembly of micelles at the critical micelle concentration (cmc) are examples of spontaneous processes the latter are characterized by a negative free-energy change, as the self-orgaiuzed product has a lower energy than the single components. ... 

Not only proteins and their oligomers, but nucleic acids as well give beautiful examples of self-organization - think of the formation of the DNA duplex, where the primary structure of the two strands determines the rules for self-assembly or the folding of t-RNA. 

Self-organization systems under thermodynamic control (spontaneous processes with a negative free-energy change), such as supramolecular complexes, crystallization, surfactant aggregation, certain nano-structures, protein folding, protein assembly, DNA duplex. 

In addition to self-assembly of protein structures, in living systems the complex maneuvers needed to achieve properly folded tertiary structures are facilitated by the function of a pre-existing protein machinery, of which, ihe molecular chaperones are an illustrative example. Chaperones are proteins that bind to and stabilize an otherwise unstable conformer of another protein, and by controlled binding and release, facilitate its correct fate in vivo. Molecular chaperones may be said to be the natural... 

---