Molten globular state

Protein folding can take place as a one-step process, where only the folded or native (N) and the unfolded (U) states are detected, or as a multistep process, where intermediate conformations occur. The so-called molten globular state has often been reported as a well-characterized intermediate conformation that shows organized... 

Figure 11.15c shows the resolved concentration profiles and spectra coming from the row-wise appended matrix containing data from the three techniques mentioned previously. The need for one additional intermediate conformation has been proven to be necessary to explain the protein folding process of a-apolactalbumin. Additionally, the thermal range of occurrence and the evolution of this intermediate can now be known. The resolved spectrum obtained for the a-apolactalbumin intermediate shows that it has an ordered secondary structure similar to the native folded protein and an unordered tertiary structure similar to the unfolded protein at high temperatures. These spectral features match the spectral description attributed to the molten globular state and provide additional evidence to confirm the presence of this species as a real intermediate conformation. 

The typical protein sequence contains a large number of hydrophobic amino acids. When these amino acids reach a specific concentration the protein collapses into a globular conformation, similar to the critical micellar concentration of detergents. This state is the result of a collapse of the protein driven by the minimization of the interaction of the hydrophobic amino acids with the aqueous environment. This condensed state is fluid in that the polymer is not in one well-defined conformation but sampling many different conformations until eventually the native conformation with the lowest free energy is found. This, usually ill-defined, state is referred to as the molten globular state. The manner in which... 

Figure 16.2 Scheme of the interaction between aMb and LUVs. At pH 7.0, the aMb is in the native form at pH 5.5, it still retains the native-like conformation but interacts with the membrane via the helix A at pH 4.0, the protein is in the molten globular state and interacts closely with the membrane via the helices A and C. The helices A-H are shown in different colors. The side chains of the two Trp in helix A are shown in gray. The sizes of the protein and the membrane are proportional. Reproduced from Ref [I] with permission from Elsevier. (See insert for color representation of the figure.)... 

Kuwajima K. The molten globule state as a clue for understanding the folding and coop-erativity of globular-protein structure. Proteins (1989) 6 87-103. 

Figure 17.1 In the protein quartet model [4], there are one ordered state and three intrinsically disordered states molten globular, premolten globular, and intrinsic coil. These states can exist under native conditions and interconvert. In the figure, the ordered protein is based on the structure of ubiquitin (PDB 1UBQ) [7], The other protein states are hypothetical models obtained by distorting the ubiquitin structure...

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