Protein energetics in maturation of the early secretory pathway.

The early secretory pathway (ESP) consisting of the endoplasmic reticulum (ER), pre-Golgi intermediates and the Golgi stack links protein synthesis to folding and vesicle trafficking to generate the membrane architecture of the eukaryotic cell. The fundamental principles that contribute to organization of the ESP remain largely unknown. We raise the possibility that assembly of the ESP is largely built on a foundation that is influenced by the kinetic and thermodynamic properties of the protein fold. Folding energetics may provide an adjustable platform for adaptor-dependent interactions with the transport machinery, suggesting the possibility that protein cargo energetics plays a central role in directing both trafficking patterns and global compartmental organization of the ESP. In this view, cargo energetics likely coordinates the composition and maturation of ER and Golgi compartments with the physiological state of the cell in different tissue and environmental settings.