Protein inactivation

Volkin DB, Klibanov AM. Minimizing protein inactivation. In Protein Function A Practical Approach, ed. TE Creighton. New York IRL Press, 1989. 

As the temperature drops still lower, some of the solutes present may also crystallize, thus being effectively removed from the solution. In some cases, individual buffer constituents can crystallize out of solution at different temperatures. This will dramatically alter the pH values of the remaining solution and, in this way, can lead to protein inactivation. 

Even with the knowledge of the reactive moieties that are suspected to trigger M BI, there are numerous potential pathways for the chemistry to lead to protein inactivation [174,196]. Differentiating these mechanisms can facilitate the generation of alternate and safer chemical scaffolds. The UV-Vis spectrophotometer has been a key instrument in activity and functional characterization for CYPs for the past 40 years, as indicated by the derivation of its name, pigment 45 0 being the signature UV band present when reduced in the presence of CO [5,197]. This technique has been... 

D. B. Volkin A. M. Klibanov, Minimising Protein Inactivation. In Protein Function A Practical Approach T. E. Creighton, Ed. IRL Press at Oxford University Press Oxford, 1989 pp 1-24. 

Fig. 1.57. Model of the regulation of translation by insulin. Insulin ( and other growth factors) activates the Akt kinase pathway (see ch. 10), whose final result is the phosphorylation of 4E-BPl, a regulatory protein of translation initiation. The 4E-BP1 protein inactivates the initation factor eIF-4E by complex formation. eIE-4E is required, together with the proteins eIE-4A and p220, for the binding of the 40S subunit of the ribosome to the cap structure of the mRNA. If the 4E-BP1 protein becomes phosphorylated as a result of insulin-mediated activation of the PI3 kinase/Akt kinase cascade, then eIE-4E is liberated from the inactive eIP-4E 4E-BPl complex and protein biosynthesis can begin.

Genes and proteins known as caretakers have an indirect influence on tumor formation. These are susceptibility genes that indirectly suppress tumor formation. An important class of caretakers includes repair proteins. Inactivation of a caretaker gene of this class leads to a sharp increase in mutation rate and is therefore equivalent to constant exposure to mutagens. 

Transmission Electron Microscopy The primary site of surfactant activity appears to be the cell membrane (25, 32). Other effects have been reported such as the denaturation of proteins, inactivation of enzymes and inhibition of mitosis. 

Volkin, D.B. and Klibanov, A.M. (1989) Minimising protein inactivation. In Protein Structure A Practical Approach (ed. Creighton, T.E.). IRL Press at Oxford University Press, Oxford. 

Keywords. Virus, Viral, Viral structure, Capsid, Dynamic, Capsid mobility, Whole virus, Intact virus, MALDI, Electrospray, Proteins, Inactivation... 

Lipophilic compounds, such as the various terpenoids, tend to associate with other hydrophobic molecules in a cell these can be biomembranes or the hydrophobic core of many proteins and of the DNA double helix [10,18,24,25]. In proteins, such hydrophobic and van der Waals interactions can also lead to conformational changes, and thus protein inactivation. A major target for terpenoids, especially saponins, is the biomembrane. Saponins (and, among them, the steroid alkaloids) can change the fluidity of biomembranes, thus reducing their function as a permeation barrier. Saponins can even make cells leaky, and this immediately leads to cell death. This can easily be seen in erythrocytes when they are attacked by saponins these cells burst and release hemoglobin (hemolysis) [1,6,17]. Among alkaloids, steroidal alkaloids (from Solanaceae) and other terpenoids have these properties. 

The decomposition of LOOH can also yield a number of highly cytotoxic products, malondialdehyde and 4-hydroxynonenal are most unpleasant among them. Lipid radicals and cytotoxic aldehydes can also cause severe damage of membrane proteins, inactivating receptors and membrane-bound enzymes [1-3]. 

The amino acid residue which is by far the most susceptible to proteolysis is Asp the cleavage of the peptide bonds in dilute acid proceeds at a rate at least 100 times that for other peptide bonds. The hydrolysis can occur at the N-terminal and/or the C-terminal peptide bonds adjacent to the Asp residue (Scheme 11.5). Cleavage of the N-terminal peptide bond proceeds via an intermediate with a six-membered ring, while cleavage of the C-terminal peptide bond is thought to involve a five-membered ring. Such peptide bond cleavage can result in protein inactivation. 

PertOfran desipramine. pertussis toxin (PTX) is elaborated by a bacterium Bordetella pertussis) and is a hexameric protein (4-5 subunits from A-B complex). It is a G-protein inactivator that binds to the ADP-ribosylation regulatory site of the G/Go family of subunits which couple negatively to adenylyl cyclase. The cellular responses blocked by PTX are varied, and typically include those due to 03 and opioid receptor type activation. The inactivation of this key regulatory unit explains some of the side-effects of whooping cough (caused by Bordetella pertussis) where production of this toxin is a main pathological factor. This toxin is an important pharmacological tool. 

Goal To determine a stability window for the target protein for easier selection and optimisation of techniques and to avoid protein inactivation during purification. 

Because inactivation of factors Va and Villa by activated protein C promotes the dissociation of the pro-teinases, cofactor protein inactivation complements the action of the proteinase inhibitors. This eliminates the protection that the proteinases have when bound to their cofactor proteins and substrates. Inactivation of proteinases by SERPINS occurs via a common mechanism that involves a Michaelis complex between the proteinase and the inhibitor (Figure 36-16). This mechanism applies to all serine proteinases of the hemostatic system, i.e., the procoagulant, anticoagulant, and fibrinolytic subsystem proteinases. 

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