Pb(II) coordination to the nonclassical zinc finger tristetraprolin: retained function with an altered fold.

Tristetraprolin (TTP) is a nonclassical CCCH zinc finger (ZF) that plays a crucial role in regulating inflammation. TTP regulates cytokine mRNAs by specific binding of its two conserved ZF domains (CysX8CysX5CysX3His) to adenylate-uridylate-rich sequences (AREs) at the 3'-untranslated region, leading to degradation of the RNA. Dysregulation of TTP in animal models has demonstrated several cytokine-related syndromes, including chronic inflammation and autoimmune disorders. Exposure to Pb(II), a prevalent environmental toxin, is known to contribute to similar pathologies, in part by disruption of and/or competition with cysteine-rich metalloproteins. TTP's role during stress as a ubiquitous translational regulator of cell signaling (and dysfunction), which may underpin various phenotypes of Pb(II) toxicity, highlights the importance of understanding the interaction between TTP and Pb(II). The impact of Pb(II) binding on TTP's fold and RNA-binding function was analyzed via UV-Vis spectroscopy, circular dichroism, X-ray absorption spectroscopy, nuclear magnetic resonance spectroscopy, and fluorescence anisotropy. A construct containing the two ZF domains of TTP (TTP-2D) bound to Pb(II) with nanomolar affinity and exhibited a different geometry and fold in comparison to Zn2-TTP-2D. Despite the altered secondary structure, Pb(II)-substituted TTP-2D bound a canonical ARE sequence more selectively than Zn2-TTP-2D. Taken together, these data suggest that Pb(II) may interfere with proper TTP regulation and hinder the cell's ability to respond to inflammation.

Characteristics of the Isu1 C-terminus in relation to [2Fe-2S] cluster assembly and ISCU Myopathy.

Mitochondrial [2Fe-2S] cluster biosynthesis is driven by the coordinated activities of the Iron-Sulfur Cluster (ISC) pathway protein machinery. Within the ISC machinery, the protein that provides a structural scaffold on which [2Fe-2S] clusters are assembled is the ISCU protein in humans; this protein is referred to as the "Scaffold" protein. Truncation of the C-terminal portion of ISCU causes the fatal disease "ISCU Myopathy", which exhibits phenotypes of reduced Fe-S cluster assembly in cells. In this report, the yeast ISCU ortholog "Isu1" has been characterized to gain a better understanding of the role of the scaffold protein in relation to [2Fe-2S] assembly and ISCU Myopathy. Here we explored the biophysical characteristics of the C-terminal region of Isu1, the segment of the protein that is truncated on the human ortholog during the disease ISCU Myopathy. We characterized the role of this region in relation to iron binding, protein stability, assembly of the ISC multiprotein complex required to accomplish Fe-S cluster assembly, and finally on overall cell viability. We determined the Isu1 C-terminus is essential for the completion of the Fe-S cluster assembly but serves a function independent of protein iron binding.

Molecular Details of the Frataxin-Scaffold Interaction during Mitochondrial Fe-S Cluster Assembly.

Iron-sulfur clusters are essential to almost every life form and utilized for their unique structural and redox-targeted activities within cells during many cellular pathways. Although there are three different Fe-S cluster assembly pathways in prokaryotes (the NIF, SUF and ISC pathways) and two in eukaryotes (CIA and ISC pathways), the iron-sulfur cluster (ISC) pathway serves as the central mechanism for providing 2Fe-2S clusters, directly and indirectly, throughout the entire cell in eukaryotes. Proteins central to the eukaryotic ISC cluster assembly complex include the cysteine desulfurase, a cysteine desulfurase accessory protein, the acyl carrier protein, the scaffold protein and frataxin (in humans, NFS1, ISD11, ACP, ISCU and FXN, respectively). Recent molecular details of this complex (labeled NIAUF from the first letter from each ISC protein outlined earlier), which exists as a dimeric pentamer, have provided real structural insight into how these partner proteins arrange themselves around the cysteine desulfurase, the core dimer of the (NIAUF)2 complex. In this review, we focus on both frataxin and the scaffold within the human, fly and yeast model systems to provide a better understanding of the biophysical characteristics of each protein alone and within the FXN/ISCU complex as it exists within the larger NIAUF construct. These details support a complex dynamic interaction between the FXN and ISCU proteins when both are part of the NIAUF complex and this provides additional insight into the coordinated mechanism of Fe-S cluster assembly.

Could Blood Pressure Phobia Go Beyond the White Coat Effect?

BACKGROUND: While it is known that excessive anxiety surrounding the measuring of blood pressure may preclude an accurate measurement, it is not known whether it could also lead to phobic avoidance behavior. METHODS: Self-reported information was collected on 125 individuals who made postings on 5 internet-based medical forums. RESULTS: Qualitative thematic analysis revealed that these individuals reported experiencing intense fear associated with the measuring of blood pressure, that was excessive or irrational and which contributed to avoidance of medical treatment and interference with life decisions. CONCLUSIONS: Based on these preliminary observations, we are speculating that these symptoms could be considered consistent with a diagnosis of a Specific Phobia. Investigations using quantitative methods, representative samples, and standardized clinical instruments need to be conducted before definitive conclusions can be reached.