Proteins - continued solubility

During the course of the symposium, several dietary factors that can influence xenobiotic metabolism were discussed in detail. Here we will attempt t summarize in the broadest terms how various classic nutrient groups might exert an influence on xenobiotic metabolism. For convenience, the dietary groups have been broken into carbohydrates, lipids, proteins, water-soluble vitamins, fat-soluble vitamins and trace elements. It is difficult to take any one group individually, and it must be kept in mind that the interactions are continuous and extremely complicated. 

Water-soluble globular proteins usually have an interior composed almost entirely of non polar, hydrophobic amino acids such as phenylalanine, tryptophan, valine and leucine witl polar and charged amino acids such as lysine and arginine located on the surface of thi molecule. This packing of hydrophobic residues is a consequence of the hydrophobic effeci which is the most important factor that contributes to protein stability. The molecula basis for the hydrophobic effect continues to be the subject of some debate but is general considered to be entropic in origin. Moreover, it is the entropy change of the solvent that i... 

Fig. 8.3 Expression of IGF-1 in transgenic chloroplasts after continuous light exposure for 13 days. IGF-1 expression is shown as a percentage of the total soluble protein. IGF-1 n is the native gene and IGF-1 s is the chloroplast codon-optimized gene.

Work on the solubility was continued by Osborne to produce the classifications of vegetable proteins that are still used. Studies of the solubility of proteins remains important both in characterising and purifying proteins. 

Vesicular proteins and lipids that are destined for the plasma membrane leave the TGN sorting station continuously. Incorporation into the plasma membrane is typically targeted to a particular membrane domain (dendrite, axon, presynaptic, postsynaptic membrane, etc.) but may or may not be triggered by extracellular stimuli. Exocytosis is the eukaryotic cellular process defined as the fusion of the vesicular membrane with the plasma membrane, leading to continuity between the intravesicular space and the extracellular space. Exocytosis carries out two main functions it provides membrane proteins and lipids from the vesicle membrane to the plasma membrane and releases the soluble contents of the lumen (proteins, peptides, etc.) to the extracellular milieu. Historically, exocytosis has been subdivided into constitutive and regulated (Fig. 9-6), where release of classical neurotransmitters at the synaptic terminal is a special case of regulated secretion [54]. 

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