Showing papers on "Polyamine binding published in 2005"

Release of long-range tertiary interactions potentiates aggregation of natively unstructured α-synuclein

Abstract: In idiopathic Parkinson's disease, intracytoplasmic neuronal inclusions (Lewy bodies) containing aggregates of the protein α-synuclein (αS) are deposited in the pigmented nuclei of the brainstem. The mechanisms underlying the structural transition of innocuous, presumably natively unfolded, αS to neurotoxic forms are largely unknown. Using paramagnetic relaxation enhancement and NMR dipolar couplings, we show that monomeric αS assumes conformations that are stabilized by long-range interactions and act to inhibit oligomerization and aggregation. The autoinhibitory conformations fluctuate in the range of nanoseconds to micro-seconds corresponding to the time scale of secondary structure formation during folding. Polyamine binding and/or temperature increase, conditions that induce aggregation in vitro, release this inherent tertiary structure, leading to a completely unfolded conformation that associates readily. Stabilization of the native, autoinhibitory structure of αS constitutes a potential strategy for reducing or inhibiting oligomerization and aggregation in Parkinson's disease.

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.

Polyamine Sensors and Methods of Using the Same

Abstract: Polyamine biosensors are disclosed, including putrescine binding biosensors, comprising a polyamine binding domain conjugated to donor and fluorescent moieties that permit detection and measurement of Fluorescence Resonance Energy Transfer upon binding polyamine. Such biosensors are useful for the detection of polyamine concentrations in vivo and in culture.