Protein Translocation across Biological Membranes and Molten Globule State on Globular Proteins.

Era Seiichi

doi:10.5360/membrane.18.318

Translocation of proteins through biological membranes is a fundamental process in transfer of exported proteins from the position of synthesis to the final destinations. Although many evidences are known about protein translocation across various membranes, it is still unclear how hydrophilic, charged proteins can translate through the hydrophobic core of a phospholipid bilayer. Particularly, there is no answer whether a protein unfolds during the transport process or whether it can translate in a folded state.<BR>In biophysical chemistry on proteins, dynamics of the folding and unfolding pathway of globular proteins have been extensively studied and have established that kinetic intermediate state on folding process might have important roles in the exact folding into a native form. Conformation of intermediate state is compact, has secondary structure similar to the native one but its tertiary structure fluctuates. Such conformation has found in several proteins and is called a “molten globule state”.<BR>The N-F transition of sodium dodecyl sulfate (SDS) -bovine serum albumin (BSA) complex (ADm; m, molar ratio of added SDS to BSA; 0<m<10) were studied by measuring CD-resolved secondary structure, ¹H-1-NMR spectra and cross-relaxation times between irradiated and observed protein protons. From these experimental evidences, the F-form of AD₁₀ may be the molten globule state which has secondary structure similar to the N-form of the complexs with fluctuating tertiary structure. In conclusion, molten globule state not only exists as a kinetic intermediate on protein folding but also is observed in such a lipid-protein complex.

Protein Translocation across Biological Membranes and Molten Globule State on Globular Proteins.

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