Polyamine binding

About: Polyamine binding is a research topic. Over the lifetime, 188 publications have been published within this topic receiving 9206 citations.

Chemical Features of the Protein Kinase CK2 Polyamine Binding Site

Abstract: Protein kinase CK2 is a ubiquitous eukaryotic Ser/Thr kinase whose catalytic activity is enhanced several times by polyamines. We have shown previously that the regulatory beta-subunit of CK2 bears a polyamine binding site located in the region Asp51-Tyr110. In the present study, we have used spermine analogs to investigate the structural requirements of the CK2 polyamine binding site. We have observed a strong correlation between the stimulations of CK2 activity by all tested polyamines and their binding efficiencies to the enzyme. As a result, spermine was found to be the most efficient stimulator of the kinase activity and the best CK2 ligand. The effect of the pH on the stimulation of CK2 activity by spermine strongly suggests the involvement of ionic interactions between the positive charges of spermine and the negative charges of acidic amino acids of the beta-subunit. Using a fusion protein made of MBP and the beta-subunit region encompassing amino acid residues Asp51-Pro110, we have studied the binding of spermine as a function of the ionic strength. We show that this region delineates a functional and autonomous domain containing a binding site involved in the interaction with the four positive charges of spermine. Altogether, these results led to the elaboration of the first model defining the crucial structural parameters of a polyamine-protein interaction at the molecular level.

A role for polyamines in retinal ganglion cell excitotoxic death

Abstract: Neuronal death due to excessive activation of N-methyl-d-aspartate (NMDA) receptors is a hallmark of neurodegenerative diseases. The polyamines: putrescine, spermine, and spermidine, bind to specific sites on the NMDA receptor and promote its activation, but their role in NMDA-induced neuronal death is ill defined. In this study, we characterized the role of polyamines in excitotoxic death of retinal ganglion cells (RGCs), a population of central neurons susceptible to NMDA-induced damage. Our data show that endogenous arginase I, the rate limiting enzyme for polyamine biosynthesis, is expressed in the intact, adult retina. Intraocular injection of NMDA visibly increased arginase I expression in Muller cells, the predominant glial cell-type in the mammalian retina. Inhibition of polyamine synthesis using di-fluoro-methyl-ornithine (DFMO) was markedly neuroprotective, while injection of exogenous polyamines in conjunction with NMDA exacerbated RGC death. Blockade of the polyamine binding sites on NMDA receptors using the non-competitive antagonist ifenprodil was neuroprotective, suggesting that polyamines contribute to excitotoxic death, at least partly, by binding to NMDA receptors. Importantly, we also demonstrate that NMDA leads to activation of both the Erk1/2 and PI3 K/Akt pathways, but only the PI3 K/Akt kinase was required for di-fluoro-methyl-ornithine-induced RGC survival. In summary, our study reveals that polyamines modulate neuronal death in the retina via different mechanisms that potentiate NMDA-triggered excitotoxicity.

Localization of spermine binding sites in 23S rRNA by photoaffinity labeling: parsing the spermine contribution to ribosomal 50S subunit functions

Abstract: Polyamine binding to 23S rRNA was investigated, using a photoaffinity labeling approach. This was based on the covalent binding of a photoreactive analog of spermine, N1-azidobenzamidino (ABA)-spermine, to Escherichia coli ribosomes or naked 23S rRNA under mild irradiation conditions. The cross-linking sites of ABA-spermine in 23S rRNA were determined by RNase H digestion and primer-extension analysis. Domains I, II, IV and V in naked 23S rRNA were identified as discrete regions of preferred cross-linking. When 50S ribosomal subunits were targeted, the interaction of the photoprobe with the above 23S rRNA domains was elevated, except for helix H38 in domain II whose susceptibility to cross-linking was greatly reduced. In addition, cross-linking sites were identified in domains III and VI. Association of 30S with 50S subunits, poly(U), tRNAPhe and AcPhe-tRNA to form a post-translocation complex further altered the cross-linking, in particular to helices H11–H13, H21, H63, H80, H84, H90 and H97. Poly(U)-programmed 70S ribosomes, reconstituted from photolabeled 50S subunits and untreated 30S subunits, bound AcPhe-tRNA in a similar fashion to native ribosomes. However, they exhibited higher reactivity toward puromycin and enhanced tRNA-translocation efficiency. These results suggest an essential role for polyamines in the structural and functional integrity of the large ribosomal subunit.

Molecular Features Associated with Polyamine Modulation of NMDA Receptors

Abstract: The effect of 1,3-diamines on basal and spermine-stimulated [3H]MK-801 binding was investigated. Systematic variations in the molecular parameters revealed that, in general, lipophilic 1,3-diamines inhibited and hydrophilic 1,3-diamines enhanced [3H]MK-801 binding in the nominal absence of glutamate and glycine. Furthermore, 1,3-diamines which were highly monoprotonated at physiologic pH were more effective in modulating basal binding (at 100 μM 1,3-diamine) than analogues which were mostly diprotonated or unprotonated. Finally, the internuclear distance between the amino nitrogens and the extent of modulation of basal [3H]MK-801 binding were correlated. Similar, but more modest, effects were seen for spermine-enhanced [3H]MK-801 binding. These results are consistent with the existence of two polyamine binding sites associated with the NMDA receptor complex. One of the sites appears to preferentially recognize lipophilic substances while the other favors hydrophilic materials. Both sites appear to recogni...