Movements of Protein

Starvation ( glucagon [ insulin) Extensive protein degradation Diabetes ( f glucagon i insulin) Protein degradation Excitement (j epinephrine)-. Protein degradation 

The glucogenic amino acids are those that produce degradation products that can be converted only to glucose (there are a bunch of these). 

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Phosphorylation Glycogen Metabolic Movements of Glycogen Fat Metabolic Movements of Fat Protein Metabolic Movements of Protein Tissue Cooperation Liver Muscle Ketone Bodies... 

The fluidity of a membrane is difficult to define but it is known to increase the rate of lateral movement of proteins in the membrane and the activity of some membrane proteins, such as ion channels and transporters of fuels (Chapter 5). Fluidity depends, in part, upon the amount and the degree of unsaturation of the fatty acids that are present... 

Membrane fluidity regulates lateral movement of proteins and lipids in the bilayer. 

The others form an extra-embryonic suspensor (Fig. 32-8B).475 The apical part of the embryo develops the shoot meristem and the central part the radial pattern of tissue layers characteristic of plants. The root meristem develops from the basal portion of the embryo. Movements of proteins that provide positional cues are involved in the development of the embryo.476,477 Early embryonic and endosperm development is largely under maternal control. Most paternal genes may be initially silent.478... 

Signal sequences usually occur at the amino terminus of polypeptides to be transported. These sequences vary in length from 10 to 40 amino acid residues and are generally characterized by the occurrence of a block of hydrophobic residues. The presence of hydrophobic residues reflects the fact that protein transport invariably involves the movement of proteins across lipid membranes. The hydrophobic residues both target the protein to the appropriate compartment and initiate penetration into the membrane. 

Table 6 shows data that attempt to distinguish between the tnuiscellular and paraceUular (between cells) pathways for peptide movement across endothelial cell monolayers. In these experiments we describe die movement of proteins in various forms across the monolayer in the presence and absence of an active... 

X-ray structures are obtained from crystalline samples. Crystallization is a laborious process, and the crystallizability of a protein is unpredictable. Some proteins do not crystallize, and X-ray diffraction is not applicable in these cases. In other cases, heavy atom derivatives needed to solve the phase problem may be difficult to obtain. Furthermore, crystals, although highly hydrated, do not represent the structure of the molecule in a true solution. Movements of protein domains are restricted in the crystaUine state. NMR methods circumvent some of these difficulties because they are applied to proteins in solution. Therefore, in addition to permitting the determination of structures, the NMR technique is useful for revealing dynamic processes such as protein protein interactions. 

Specihc membrane and membrane-associated proteins also control the organelle traffic and fusion events that are associated with the movement of proteins between different intracellular compartments. Membrane proteins of the secretory and endocytic pathways depend on sorting signals that reside in their cytoplasmic domains. Many proteins exhibit multiple signals that determine their passage along these diverse pathways. Therefore, the steady-state distribution of any given membrane... 

The diffusion coefficients and translational movements of proteins are important in considering the release of proteins from hydrogel matrix devices and other delivery vehicles, and in membrane transport, as far as this can be considered to be a passive diffusion process. Changes in shape during membrane transport in a lipid environment may also have to be considered. Table 11.6 gives some values of diffusion coefficient of a number of therapeutic peptides and proteins. 

Brightman, M.W. (1968) The intracerebral movement of proteins injected into blood and cerebrospinal fluid of mice. Progress in Brain Research, 29, 19-40. 

Molecular dynamics methods are primarily used for the refinement of structural models (Li et al., 1997) or the analysis of molecular interactions (Cappelli et al., 1996 Kothekar et al., 1998). In both cases the time scales to be simulated are within range of current computing technology. Another application area is the study of allosteric movements of proteins (Tanner et al., 1993). Molecular Dynamics approaches to protein-ligand docking are described in Chapter 7 of Volume I. 

A EXPERIMENTAL FIGURE 5-6 Fluorescence recovery after photobleaching (FRAP) experiments can quantify the lateral movement of proteins and lipids within the plasma membrane, (a) Experimental protocol. Step H Cells are first labeled with a fluorescent reagent that binds uniformly to a specific membrane lipid or protein. Step B A laser light is then focused on a small area of the surface, irreversibly bleaching the bound reagent and thus reducing the fluorescence in the illuminated area. Step B In time, the fluorescence of the bleached patch increases as unbleached fluorescent surface molecules diffuse into it and bleached ones diffuse outward. The extent of recovery of fluorescence in the bleached patch is... 

As the syncytial fly embryo becomes cellular and undergoes gastrulation, the movement of proteins and mRNAs through the common cytoplasm of a syncytium is over. Further cell-fate specification is controlled primarily by cells communicating with one another through secreted extracellular signals. In this section, we examine how three signaling path-... 

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