The C19S Substitution Enhances the Stability of Hepcidin While Conserving Its Biological Activity.

Hepcidin, the key hormone of iron homeostasis is responsible for lowering the serum iron level through its interaction with iron exporter ferroportin. Thus, hepcidin agonists provide a promising opportunity in the treatment of iron disorders caused by lacking or decreased hepcidin expression. We investigated the importance of each of the eight highly conserved cysteines for the biological activity of hepcidin.

Cardiac leiomodin2 binds to the sides of actin filaments and regulates the ATPase activity of myosin.

Leiomodin proteins are vertebrate homologues of tropomodulin, having a role in the assembly and maintenance of muscle thin filaments. Leiomodin2 contains an N-terminal tropomodulin homolog fragment including tropomyosin-, and actin-binding sites, and a C-terminal Wiskott-Aldrich syndrome homology 2 actin-binding domain. The cardiac leiomodin2 isoform associates to the pointed end of actin filaments, where it supports the lengthening of thin filaments and competes with tropomodulin.

Photochemistry of Wild-Type and N378D Mutant E. coli DNA Photolyase with Oxidized FAD Cofactor Studied by Transient Absorption Spectroscopy.

DNA photolyases (PLs) and evolutionarily related cryptochrome (CRY) blue-light receptors form a widespread superfamily of flavoproteins involved in DNA photorepair and signaling functions. They share a flavin adenine dinucleotide (FAD) cofactor and an electron-transfer (ET) chain composed typically of three tryptophan residues that connect the flavin to the protein surface. Four redox states of FAD are relevant for the various functions of PLs and CRYs: fully reduced FADH(-) (required for DNA photorepair), fully oxidized FADox (blue-light-absorbing dark state of CRYs), and the two semireduced radical states FAD(.

Prohepcidin binds to the HAMP promoter and autoregulates its own expression.

Hepcidin is the major regulatory peptide hormone of iron metabolism, encoded by the HAMP (hepcidin antimicrobial peptide) gene. Hepcidin is expressed mainly in hepatocytes, but is also found in the blood in both a mature and prohormone form. Although, the function of mature hepcidin and the regulation of the HAMP gene have been extensively studied, the intracellular localization and the fate of prohepcidin remains controversial.

Conformational dynamics of titin PEVK explored with FRET spectroscopy.

The proline-, glutamate-, valine-, and lysine-rich (PEVK) domain of the giant muscle protein titin is thought to be an intrinsically unstructured random-coil segment. Various observations suggest, however, that the domain may not be completely devoid of internal interactions and structural features. To test the validity of random polymer models for PEVK, we determined the mean end-to-end distances of an 11- and a 21-residue synthetic PEVK peptide, calculated from the efficiency of the fluorescence resonance energy transfer (FRET) between an N-terminal intrinsic tryptophan donor and a synthetically added C-terminal IAEDANS acceptor obtained in steady-state and time-resolved experiments.

Dynamic strength of titin's Z-disk end.

Titin is a giant filamentous protein traversing the half sarcomere of striated muscle with putative functions as diverse as providing structural template, generating elastic response, and sensing and relaying mechanical information. The Z-disk region of titin, which corresponds to the N-terminal end of the molecule, has been thought to be a hot spot for mechanosensing while also serving as anchorage for its sarcomeric attachment. Understanding the mechanics of titin's Z-disk region, particularly under the effect of binding proteins, is of great interest.

Spatially and temporally synchronized atomic force and total internal reflection fluorescence microscopy for imaging and manipulating cells and biomolecules.

The atomic force microscope is a high-resolution scanning-probe instrument which has become an important tool for cellular and molecular biophysics in recent years but lacks the time resolution and functional specificities offered by fluorescence microscopic techniques. To exploit the advantages of both methods, here we developed a spatially and temporally synchronized total internal reflection fluorescence and atomic force microscope system. The instrument, which we hereby call STIRF-AFM, is a stage-scanning device in which the mechanical and optical axes are coaligned to achieve spatial synchrony.

Progesterone-induced blocking factor activates STAT6 via binding to a novel IL-4 receptor.

Progesterone-induced blocking factor (PIBF) induces Th2-dominant cytokine production. Western blotting and EMSA revealed phosphorylation as well as nuclear translocation of STAT6 and inhibition of STAT4 phosphorylation in PIBF-treated cells. The silencing of STAT6 by small interfering RNA reduced the cytokine effects.

Reversible mechanical unzipping of amyloid beta-fibrils.

Amyloid fibrils are self-associating filamentous structures, the deposition of which is considered to be one of the most important factors in the pathogenesis of Alzheimer's disease and various other disorders. Here we used single molecule manipulation methods to explore the mechanics and structural dynamics of amyloid fibrils. In mechanically manipulated amyloid fibrils, formed from either amyloid beta (Abeta) peptides 1-40 or 25-35, beta-sheets behave as elastic structures that can be "unzipped" from the fibril with constant forces.

Differential actin binding along the PEVK domain of skeletal muscle titin.

Parts of the PEVK (Pro-Glu-Val-Lys) domain of the skeletal muscle isoform of the giant intrasarcomeric protein titin have been shown to bind F-actin. However, the mechanisms and physiological function of this are poorly understood. To test for actin binding along PEVK, we expressed contiguous N-terminal (PEVKI), middle (PEVKII), and C-terminal (PEVKIII) PEVK segments of the human soleus muscle isoform.

Stretching and visualizing titin molecules: combining structure, dynamics and mechanics.

The details of the global and local structure and function of titin, a giant filamentous intrasarcomeric protein are largely undiscovered. Here we discuss a combination of bulk-solution and novel single-molecule techniques that may lend unique insights into titin's molecular dynamic, structural and mechanical characteristics.

Flow cytometric analysis of DMBA-induced early in vivo ras expression.

According to recent publications 7,12-dimethylbenz[a]anthracene (DMBA) induces not only mammary cancer but also leukemia in Long-Evans (LE) rats. After treatment with DMBA, trisomy of the chromosome bearing N-ras and mutations in the codon 61 of different ras family genes are frequent. These alterations are already visible within 48 hours.