Biography:

In the past Peter Friedrich has collaborated on articles with Judit Kramer and PETER FRIEDRICH. One of their most recent publications is Quantitative evaluation of gel electrophoretic patterns by videodensitometry. Which was published in journal Analytical Biochemistry.

More information about Peter Friedrich research including statistics on their citations can be found on their Copernicus Academic profile page.

Peter Friedrich's Articles: (14)

Quantitative evaluation of gel electrophoretic patterns by videodensitometry

AbstractVideodensitometry based on television technique has been shown to be suitable for recording gel electrophoretic patterns. Its speed of operation is about 60 times as fast as that of conventional densitometers, whereas the patterns recorded are practically the same.

Quantitative evaluation of gel electrophoretic patterns by videodensitometry

AbstractVideodensitometry based on television technique has been shown to be suitable for recording gel electrophoretic patterns. Its speed of operation is about 60 times as fast as that of conventional densitometers, whereas the patterns recorded are practically the same.

Quantitative evaluation of gel electrophoretic patterns by videodensitometry

AbstractVideodensitometry based on television technique has been shown to be suitable for recording gel electrophoretic patterns. Its speed of operation is about 60 times as fast as that of conventional densitometers, whereas the patterns recorded are practically the same.

Quantitative evaluation of gel electrophoretic patterns by videodensitometry

AbstractVideodensitometry based on television technique has been shown to be suitable for recording gel electrophoretic patterns. Its speed of operation is about 60 times as fast as that of conventional densitometers, whereas the patterns recorded are practically the same.

CHAPTER 3 - INTRAMOLECULAR ORGANIZATION: THE QUATERNARY STRUCTURE OF ENZYMES

Publisher SummaryThis chapter focuses on the quaternary structure of enzymes. This structure of enzymes covers oligomeric enzymes and complex enzymes. An oligomeric protein is composed of identical subunits called protomers. On closer inspection, this statement must be qualified by saying that the protomers need not be strictly identical, only quasi-identical. The overwhelming majority of oligomeric enzymes are dimers and tetramers. The chapter discusses the number of subunits in oligomeric enzymes and biological roles of oligomeric structure. The next stage in the structural organization of enzymes after true oligomers is occupied by complex enzymes. This term is used to denote enzymes consisting of catalytic and non-catalytic (as a rule, regulatory) subunits. Complex enzymes may be regarded as allosteric enzymes in which the domain building up the binding site for the regulatory effector(s) is separated from the domain accommodating the catalytic site in the sense that it lies in a distinct polypeptide chain. The chapter discusses regulation of these enzymes through non-catalytic subunits.

CHAPTER 4 - INTERMOLECULAR ORGANIZATION: MULTIENZYME SYSTEMS

Publisher SummaryThis chapter focuses on multienzyme systems. In the living cell, each enzyme is part of a multienzyme system responsible for running a metabolic pathway which, in turn, is the component of an even larger network, finally building up to what is displayed on the popular and inextricable metabolic maps. Evolution worked at the level of the organism, the viability of which was the resultant of an interplay of the numerous pathways. Hence, from the organism's point of view, be it a single cell or a multicellular being, it was not the excellence of any single enzyme, but rather the controlled output of the enzyme system that was crucial. It seems, therefore, obvious that the multienzyme systems existing in living organisms must possess a high degree of organization. There are two levels of organization, namely, the purely functional and the structural–functional ones. Functional organization means that each enzyme has been tailored, evolved in structure, to have functional properties that satisfactorily mesh with those of other enzymes in the same and other systems. Thus, functional organization involves not only the kinetic complementarity of sequentially consecutive enzymes but also remote effects underlying feedback inhibition or forward activation via allosteric transitions.

Regular ArticleDomain III of Calpain Is a Ca2+-Regulated Phospholipid-Binding Domain☆

AbstractThe X-ray structure of m-calpain shows that domain III of the large subunit is structurally related to C2 domains, Ca2+-regulated lipid binding modules in many enzymes. To address whether this structural similarity entails functional analogy, we have characterized recombinant domain III from rat μ- and m-calpain and Drosophila CALPB. In a Ca2+ overlay assay domain III displays a large capacity for Ca2+ binding, commensurable with that of domain IV, the principal Ca2+-binding domain of calpains. The amount of Ca2+ bound to domain III increases 2- to 10-fold upon the addition of liposomes containing 20–40% di- and triphosphoinositides. Conversely, phospholipid-binding in spin-column size-exclusion chromatography is significantly promoted by Ca2+, in a manner similar to known C2 domains. These results suggest that domain III might be the primary lipid binding site of calpain and may play a decisive role in orchestrating Ca2+- and lipid activation of the enzyme.

Breakthroughs and ViewsThe intriguing Ca2+ requirement of calpain activation

AbstractMammalian ubiquitous μ- and m-calpains, as well as their Drosophila homologs, Calpain A and Calpain B, are Ca2+-activated cytoplasmic proteases that act by limited proteolysis of target proteins. Calpains are thought to be part of many cellular signaling pathways. These enzymes, however, require such high Ca2+ concentration for half-maximal activation in vitro, [Ca2+]0.5, that hardly ever occurs in intact cells. This major dilemma has pervaded the literature on calpains for decades. In this paper several considerations are put forward that challenge the orthodox view and envisage mechanisms that may govern calpain action in vivo. The “unphysiologically” high Ca2+ demand for activation may turn out to be an evolutionarily adjusted safety device.

Calpain as a multi-site regulator of cell cycle

AbstractCalpain has long been implicated in the regulation of cell cycle, mostly based on studies with inhibitors that lack strict specificity toward the enzyme. Further, previous work has primarily focused on one particular point, the G1 checkpoint, and made no attempt at dissecting the full cycle in terms of calpain action. To extend and complement these findings, we tested the effect of a specific inhibitor, PD 150606, on granulocyte-macrophage-colony stimulating factor (GM-CSF)-stimulated human TF-1 cells by flow cytometry following single- and double labelling by propidium iodide and bromodeoxyuridine. Using a new algorithm of analysis, we determined the time-dependence of the absolute number of cells leaving G1, S and G2M phases following the application of the inhibitor. Our results point to the simultaneous involvement of calpain activity in promoting the cycle at the G1 checkpoint and somewhere in the G2M compartment. Furthermore, the inhibitor significantly impedes the progress of cells through the S phase, indicating calpain activity in S phase checkpoint signalling. Overall, our analysis suggests that calpain regulates the cell cycle at more points than previously thought.

The Role of Dimerization in Prion Replication

AbstractThe central theme in prion diseases is the conformational transition of a cellular protein from a physiologic to a pathologic (so-called scrapie) state. Currently, two alternative models exist for the mechanism of this autocatalytic process; in the template assistance model the prion is assumed to be a monomer of the scrapie conformer, whereas in the nucleated polymerization model it is thought to be an amyloid rod. A recent variation on the latter assumes disulfide reshuffling as the mechanism of polymerization. The existence of stable dimers, let alone their mechanistic role, is not taken into account in either of these models. In this paper we review evidence supporting that the dimerization of either the normal or the scrapie state, or both, has a decisive role in prion replication. The contribution of redox changes, i.e., the temporary opening and possible rearrangement of the intramolecular disulfide bridge is also considered. We present a model including these features largely ignored so far and show that it adheres satisfactorily to the observed phenomenology of prion replication.

Research reportIschemia-induced increase in long-term potentiation is warded off by specific calpain inhibitor PD150606

AbstractIn the present study, the effect of specific, membrane-permeable calpain inhibitor, PD150606, was analysed on synaptic efficacy in in vitro brain slices experiments after ischemic insult of rats in vivo, and on cell viability in a glutamate excitotoxicity test in mouse cell culture. Bilateral common carotid artery ligation (BCCL) for 24 h markedly increased calpain activity and enhanced LTP induction in rat hippocampus, although the CA1 layer significantly shrank. The enhancement of LTP could be diminished by short-term application of PD150606 (40 μM) into the perfusion solution. Intracerebroventricular administration of PD150606 (100 μM) parallel with ischemic insult prevented LTP and effectively inhibited hippocampal calpain activity. Intracerebroventricularly applied PD150606 inhibited the CA1 layer shrinkage after common carotid ligation. High level of exogenous glutamate caused marked decrease of cell viability in mouse cerebellar granule cell cultures, which could be partly warded off by 20 μM PD150606. Our data witness that calpain action is intricately involved in the regulation of synaptic efficacy.

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