Evidence for absence of an interaction between purified 3-phosphoglycerate kinase and glyceraldehyde-3-phosphate dehydrogenase

Phosphofructokinase relocalizes into subcellular compartments with liquid-like properties in vivo

Although much is known about the biochemical regulation of glycolytic enzymes, less is understood about how they are organized inside cells. We systematically examine the dynamic subcellular localization of glycolytic protein phosphofructokinase-1/PFK-1.1 in Caenorhabditis elegans. We determine that endogenous PFK-1.1 localizes to subcellular compartments in vivo. In neurons, PFK-1.1 forms phase-separated condensates near synapses in response to energy stress from transient hypoxia. Restoring animals to normoxic conditions results in cytosolic dispersion of PFK-1.1. PFK-1.1 condensates exhibit liquid-like properties, including spheroid shapes due to surface tension, fluidity due to deformations, and fast internal molecular rearrangements. Heterologous self-association domain cryptochrome 2 promotes formation of PFK-1.1 condensates and recruitment of aldolase/ALDO-1. PFK-1.1 condensates do not correspond to stress granules and might represent novel metabolic subcompartments. Our studies indicate that glycolytic protein PFK-1.1 can dynamically form condensates in vivo.

Loose interaction between glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate kinase revealed by fluorescence resonance energy transfer-fluorescence lifetime imaging microscopy in living cells

Loose interaction between the glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoglycerate kinase (PGK) was visualized in living CHO-K1 cells by fluorescence resonance energy transfer (FRET), using time-domain fluorescence lifetime imaging microscopy. FRET between active tetrameric subunits of GAPDH linked to cerulean or citrine was observed, and this FRET signal was significantly attenuated by coexpression of PGK. Also, direct interaction between GAPDH-citrine and PGK-cerulean was observed by FRET. The strength of FRET signals between them was dependent on linkers that connect GAPDH to citrine and PGK to cerulean. A coimmunoprecipitation assay using hemagglutinin-tagged GAPDH and FLAG-tagged PGK coexpressed in CHO-K1 cells supported the FRET observation. Taken together, these results demonstrate that a complex of GAPDH and PGK is formed in the cytoplasm of living cells.

Use of protein-protein interactions in affinity chromatography

Biospecific recognition between proteins is a phenomenon that can be exploited for designing affinity-chromatographic purification systems for proteins. In principle, the approach is straightforward, and there are usually many alternative ways, since a protein can be always found which binds specifically enough to the desired protein. Routine immunoaffinity chromatography utilizes the recognition of antigenic epitopes by antibodies. However, forces involved in protein-protein interactions as well the forces keeping the three-dimensional structures of proteins intact are complicated, and proteins are easily unfolded by various factors with unpredictable results. Because of this and because of the generally high association strength between proteins, the correct adjustment of binding forces between an immobilized protein and the protein to be purified as well as the release of bound proteins in biologically active form from affinity complexes are the main problem. Affinity systems involving interactions like enzyme-enzyme, subunit-oligomer, protein-antibody, protein-chaperone and the specific features involved in each case are presented as examples. This article also aims to sketch prospects for further development of the use of protein-protein interactions for the purification of proteins.

Application of short column gel permeation in the study of protein-protein interactions

A simple and rapid procedure based on the gel filtration principle is described together with its applicability to the study of protein-protein interactions including subunit-subunit and enzyme-enzyme interactions. Using this procedure, it is shown that phosphoglycerate kinase (PGK) and glyceraldehyde-3-phosphate dehydrogenase (GPDH) interact with a stoichiometry of one PGK molecule combining with one monomeric subunit of GPDH. This interaction has been observed with both enzymes being from the same, as well as from different, species. The Kd values for rabbit muscle PGK and porcine muscle GPDH complex and that for the rabbit muscle PGK and yeast GPDH complex are found to be (4.5 +/- 2.0) x 10(-7) M and (6.5 +/- 1.7) x 10(-7) M, respectively. The specificity of bienzyme association is stronger when enzymes are from the same species than when they are from different species.

Phosphoglycerate-kinase-glyceraldehyde-3-phosphate-dehydrogenase interaction. Molecular mass studies

When rabbit muscle phosphoglycerate kinase (PGK; a 48-kDa monomeric protein) and glyceraldehyde-3-phosphate dehydrogenase (GraPDH; a 145-kDa homotetrameric protein) are present together in solution in the proportion of 1 mol PGK/1 mol GraPDH monomer (total protein 0.2-1.0 mg/ml), an 80--82-kDa protein species is observed by gel-penetration (dilution factor) method and by the conventional procedure of elution from a gel column. Individually, PGK and GraPDH do not exhibit any self association or dissociation in the concentration range employed. Electrophoresis of the 80-82-kDa peak eluted from the gel column shows a single protein band with mobility intermediate between those of GraPDH and PGK. In titration experiments by the gel-penetration method, plots of dilution factor of PGK (or GraPDH) activity versus GraPDH (or PGK) concentration shows two linear portions intersecting at approximately 1 mol GraPDH monomer/1 mol PGK. From the molecular-mass values and the titration experiments, it has been suggested that, in solution, these enzymes form a complex consisting of 1 molecule of PGK and one monomeric subunit of GraPDH (expected molecular mass 84 kDa). Its dissociation constant has been estimated to be equal to or less than 13 nM. The complex is dissociated in the presence of KCl or NADH, with approximately half dissociation at 0.1 M salt or 0.25 mM NADH. At 0.1 M KCl, the complex is completely dissociated by adding ATP, NADH or 3-phosphoglycerate. AMP, ADP, NAD+, glyceraldehyde-3-phosphate, phosphate ions and fructose-1,6-bisphosphate reverse the effect of KCl.

Kinetic misinterpretation of a coupled enzyme reaction can lead to the assumption of an enzyme-enzyme interaction. The example of 3-phospho-D-glycerate kinase and glyceraldehyde-3-phosphate dehydrogenase couple

The time course of the conversion of 3-phospho-D-glycerate (GriP) to glyceraldehyde-3-phosphate (GraP) catalyzed by 3-phospho-D-glycerate kinase (GriP kinase) and glyceraldehyde-3-phosphate dehydrogenase (GraPDH) couple has been reinvestigated. The dependence of the steady-state rate on the dehydrogenase concentration is fully compatible with the consecutive nature of the reaction and therefore is not necessarily related to a complex formation of the two enzymes. To derive a Kd value of a bienzyme complex, as was done by Sukhodolets et al. [Sukhodolets, M. V., Muronetz, V. I. & Nagradova, N. K. (1987) Biochem. Int. 15, 373-379], is basically erroneous. In contrast with some previous reports, the maximal activity of GriP kinase is not influenced by the auxiliary enzyme present in the coupled assay system. Thus, no special accelerating effect can be attributed to GraPDH. 1,3-Bisphospho-D-glycerate (GriP2) bound to GriP kinase does not seem to be a substrate for GraPDH, providing evidence against channelling of GriP2 between the two enzymes.

A reappraisal of the binding of cytosolic enzymes to erythrocyte membranes

Several cytosolic proteins have been shown to be associated with hypotonic erythrocyte ghosts via electrostatic interactions with the anion transport band 3 protein. This article considers the problems of demonstrating binding under physiological conditions and reviews the evidence for the relevance of enzyme binding to the membrane for the regulation of glycolysis. The hypotheses for the existence of topological and sequential multienzyme complexes of the glycolytic enzymes in erythrocytes are also discussed.

Association of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase. The biochemical and electron-microscopic evidence

Rabbit muscle glyceraldehyde-3-phosphate dehydrogenase covalently bound to Sepharose was shown to form a complex with soluble 3-phosphoglycerate kinase. The strength of the association appeared to depend upon the functional state of both enzymes. The holoform of the dehydrogenase exhibited a lower affinity for the kinase than the enzyme-3-phosphoglycerol.NADH complex. The substrate-free 3-phosphoglycerate kinase associated much stronger with the acylated dehydrogenase than the kinase in complex with 1,3-diphosphoglycerate. Electron-microscopic evidence for the association of the soluble acyl-glyceraldehyde-3-phosphate dehydrogenase.NADH complex and 3-phosphoglycerate kinase was also obtained.

Changes in the redox state of neuroblastoma cells after manganese exposure

The toxicological effects of manganese chloride on the redox state of thiols and on the lipid peroxidation in cultures of the neuroblastoma clone N1E 115 were studied. The cell cultures were exposed, after a stationary growth phase was attained, to manganese chloride (25-100 microM) for up to 9 days. The non-protein thiols decreased at the most 27% as compared to the controls. Significant effects were obtained at all manganese concentrations tested. The total thiol content was maximally reduced by 40%. This reduced thiol content was also reflected in a lowered activity of the thiolenzyme, glyceraldehyde-3-phosphate dehydrogenase in manganese exposed cells. In addition the lipid peroxide level in the cells was decreased during the manganese treatment.

On the Application of Cultured Neuronal Cell Lines in Neurotoxicological Studies: Implications of Acrylamide-induced Neurite Disintegration

Summary

Cultures of the mouse neuroblastoma cell line C1300, clone N1E115 were exposed to acrylamide at 3.5 x 10-4M for 14 days (subacute situation) or at 2.8 x 10-3 M for 24 hr (acute situation).

In the subacute situation the total uptake of 2-deoxy-D-glucose was stimulated. This could be explained by an increase in both the non-specific diffusion and the specific transport. The activity of the glycolytic enzyme, enolase (EC4.2.1.11), was unaffected by exposure to acrylamide, whereas the activity of glyceraldehyde-3-phosphate-dehydrogenase (EC1.2.1.12) was inhibited. Acrylamide had a marked stimulating effect on the respiratory activity of the cells, whereas the incorporation of tritiated leucine remained unchanged. Furthermore, membrane integrity was maintained throughout the acrylamide exposure as judged by an unchanged rate of 2-deoxy-D-glucose-6-phosphate efflux. Corresponding results were obtained in the acute situation. In N1E115 cultures and under the experimental conditions used in this work acrylamide caused neurite degeneration resembling distal axonopathy in vivo. It is suggested that these degenerative changes are not due to a general intoxication of the cells, but rather to a specific effect. Consequently, the N1E115 cell line might be useful in studies of chemically-induced axonopathies.