Dynamics study on the anti-human immunodeficiency virus chemokine viral macrophage-inflammatory protein-II (VMIP-II) reveals a fully monomeric protein

Encoded by Kaposi's sarcoma-associated herpesvirus, viral macrophage-inflammatory protein-II (VMIP-II) is unique among CC chemokines in that it has been shown to bind to the CXC chemokine receptor CXCR4 as well as to a variety of CC chemokine receptors. This unique binding ability allows vMIP-II to block infection by a wide range of human immunodeficiency virus type I (HIV-1) strains, but the structural and dynamic basis for this broad range of binding is not known. 15N T1, T2 and 15N[-HN] nuclear Overhauser effect (NOE) values of vMIP-II, determined through a series of heteronuclear multidimensional nuclear magnetic resonance (NMR) experiments, were used to obtain information about the backbone dynamics of the protein. Whereas almost all chemokine structures reveal a dimer or multimer, vMIP-II has a rotational correlation time (tauc) of 4.7 +/- 0.3 ns, which is consistent with a monomeric chemokine. The rotational diffusion anisotropy, D parallel/D perpendicular, is approximately 1.5 +/- 0.1. The conformation of vMIP-II is quite similar to other known chemokines, containing an unstructured N-terminus followed by an ordered turn, three beta-strands arranged in an antiparallel fashion, and one C-terminal alpha-helix that lies across the beta-strands. Most of the protein is well-ordered on a picosecond time scale, with an average order parameter S2 (excluding the N-terminal 13 amino acids) of 0.83 +/- 0. 09, and with even greater order in regions of secondary structure. The NMR data reveal that the N-terminus, which in other chemokines has been implicated in receptor binding, extends like a flexible tail in solution and possesses no secondary structure. The region of the ordered turn, including residues 25-28, experiences conformational exchange dynamics. The implications of these NMR data to the broad receptor binding capability of vMIP-II are discussed.     

The DNA binding properties of Saccharomyces cerevisiae Rad51 protein

Saccharomyces cerevisiae Rad51 protein is the paradigm for eukaryotic ATP-dependent DNA strand exchange proteins. To explain some of the unique characteristics of DNA strand exchange promoted by Rad51 protein, when compared with its prokaryotic homologue the Escherichia coli RecA protein, we analyzed the DNA binding properties of the Rad51 protein. Rad51 protein binds both single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) in an ATP- and Mg2+-dependent manner, over a wide range of pH, with an apparent binding stoichiometry of approximately 1 protein monomer per 4 (+/-1) nucleotides or base pairs, respectively. Only dATP and adenosine 5'-gamma-(thiotriphosphate) (ATPgammaS) can substitute for ATP, but binding in the presence of ATPgammaS requires more than a 5-fold stoichiometric excess of protein. Without nucleotide cofactor, Rad51 protein binds both ssDNA and dsDNA but only at pH values lower than 6.8; in this case, the apparent binding stoichiometry covers the range of 1 protein monomer per 6-9 nucleotides or base pairs. Therefore, Rad51 protein displays two distinct modes of DNA binding. These binding modes are not inter-convertible; however, their initial selection is governed by ATP binding. On the basis of these DNA binding properties, we conclude that the main reason for the low efficiency of the DNA strand exchange promoted by Rad51 protein in vitro is its enhanced dsDNA-binding ability, which inhibits both the presynaptic and synaptic phases of the DNA strand exchange reaction as follows: during presynapsis, Rad51 protein interacts with and stabilizes secondary structures in ssDNA thereby inhibiting formation of a contiguous nucleoprotein filament; during synapsis, Rad51 protein inactivates the homologous dsDNA partner by directly binding to it.     

Tryptase mediates hyperresponsiveness in isolated guinea pig bronchi

Hyperresponsiveness of airway smooth muscle to allergens and environmental factors has long been associated with the pathophysiology of asthma. Tryptase, a serine protease of lung mast cells, has been implicated as one of the mediators involved in the induction of hyperresponsiveness. As a consequence, tryptase inhibitors have become the subject of study as potential novel therapeutic agents for asthma. Secretory leukocyte protease inhibitor (SLPI) is a naturally occurring protein of human airways which exhibits anti-tryptase activity. To assess the potential therapeutic utility of SLPI in asthma, its effects were evaluated using in vitro and ex vivo models of airway hyperresponsiveness and compared with the effects of the small molecule tryptase inhibitor APC-366. Our results demonstrate that SLPI inhibits tryptase-mediated hyperresponsiveness in vitro and attenuates the hyperresponsiveness observed in airway smooth muscle from antigen-sensitized animals subjected to antigen exposure. The small molecule tryptase inhibitor APC-366 has a similar inhibitory effect. Thus, tryptase appears to be a significant contributor to the development of hyperresponsiveness in these models. To the extent that tryptase contributes to the development and progression of asthma, SLPI may possess therapeutic potential in this disease setting.     

A probable explanation for mild extra-articular manifestations in Indian patients of rheumatoid arthritis: a preliminary study

The combination of a total lower lip, chin, and anterior mandibular defect following cancer resection is an extremely complex problem that requires a sequence of operations to optimize functional and aesthetic results. One patient is presented in whom the defect was reconstructed with a free fibular flap followed by a series of ancillary procedures using both modern and traditional techniques. At the time of tumor ablation, the through-and-through oromandibular defect was reconstructed with a fibular osteocutaneous flap. The lower lip and gingivolabial sulcus was reconstructed later with a tongue flap. Tissue expansion was subsequently used to replace the fibular skin with expanded submental hair-bearing skin. A polyethylene implant was added later to the fibular bone for chin augmentation. Subsequently the lower lip was supported with a tendinous graft suspended to the anterior masseter bilaterally. Lastly, the vermilion border was elevated by removing a rim of the tongue flap and covering the secondary wound with a full-thickness skin graft. At the end of the reconstructive procedures, lip seal and oral aperture were good with no drooling and excellent speech.     

The Mainz pouch II

The Mainz pouch II procedure has proved to be a substantial modification of the classical technique of ureterosigmoidostomy at many institutions. To date we have used this procedure in 72 patients, including 15 children. Detubularization causes a low pressure and eliminates high-pressure contractions. Without the risk of compromising the blood supply the pouch is fixed at the promontory which reduces the risk of ureteral kinking and upper urinary tract dilatation as it is sometimes observed after ureterosigmoidostomy. The technique is not only indicated in cases of failed ureterosigmoidostomy but also for primary urinary diversion. Of the 72 patients operated, all are evaluable with a follow-up of 1-31 months. All patients are continent during the daytime with a mean emptying frequency of 5. All but one elderly woman are dry at night with a mean frequency of 1. The described urodynamic/rectodynamic evaluation enables a reliable prediction of postoperative continence. With the reservoir full the basal pressure was 24 cm H2O and the highest peak pressure recorded was 35 cm H2O.