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41.
42.
Selective inhibition of the collagenolytic activity of human cathepsin K by altering its S2 subsite specificity 总被引:3,自引:0,他引:3
The primary specificity of papain-like cysteine proteases (family C1, clan CA) is determined by S2-P2 interactions. Despite the high amino acid sequence identities and structural similarities between cathepsins K and L, only cathepsin K is capable of cleaving interstitial collagens in their triple helical domains. To investigate this specificity, we have engineered the S2 pocket of human cathepsin K into a cathepsin L-like subsite. Using combinatorial fluorogenic substrate libraries, the P1-P4 substrate specificity of the cathepsin K variant, Tyr67Leu/Leu205Ala, was determined and compared with those of cathepsins K and L. The introduction of the double mutation into the S2 subsite of cathepsin K rendered the unique S2 binding preference of the protease for proline and leucine residues into a cathepsin L-like preference for bulky aromatic residues. Homology modeling and docking calculations supported the experimental findings. The cathepsin L-like S2 specificity of the mutant protein and the integrity of its catalytic site were confirmed by kinetic analysis of synthetic di- and tripeptide substrates as well as pH stability and pH activity profile studies. The loss of the ability to accept proline in the S2 binding pocket by the mutant protease completely abolished the collagenolytic activity of cathepsin K whereas its overall gelatinolytic activity remained unaffected. These results indicate that Tyr67 and Leu205 play a key role in the binding of proline residues in the S2 pocket of cathepsin K and are required for its unique collagenase activity. 相似文献
43.
The regulation of cation content is critical for cell growth. However, the molecular mechanisms that gate the systems that control K+ movements remain unclear. KTN is a highly conserved cytoplasmic domain present ubiquitously in a variety of prokaryotic and eukaryotic K+ channels and transporters. Here we report crystal structures for two representative KTN domains that reveal a dimeric hinged assembly. Alternative ligands NAD+ and NADH block or vacate, respectively, the hinge region affecting the dimer's conformational flexibility. Conserved, surface-exposed hydrophobic patches that become coplanar upon hinge closure provide an assembly interface for KTN tetramerization. Mutational analysis using the KefC system demonstrates that this domain directly interacts with its respective transmembrane constituent, coupling ligand-mediated KTN conformational changes to the permease's activity. 相似文献
44.
Choe H Burtnick LD Mejillano M Yin HL Robinson RC Choe S 《Journal of molecular biology》2002,324(4):691-702
Gelsolin participates in the reorganization of the actin cytoskeleton that is required during such phenomena as cell movement, cytokinesis, and apoptosis. It consists of six structurally similar domains, G1-G6, which are arranged at resting intracellular levels of calcium ion so as to obscure the three actin-binding surfaces. Elevation of Ca(2+) concentrations releases latches within the constrained structure and produces large shifts in the relative positioning of the domains, permitting gelsolin to bind to and sever actin filaments. How Ca(2+) is able to activate gelsolin has been a major question concerning the function of this protein. We present the improved structure of the C-terminal half of gelsolin bound to monomeric actin at 3.0 A resolution. Two classes of Ca(2+)-binding site are evident on gelsolin: type 1 sites share coordination of Ca(2+) with actin, while type 2 sites are wholly contained within gelsolin. This structure of the complex reveals the locations of two novel metal ion-binding sites in domains G5 and G6, respectively. We identify both as type 2 sites. The absolute conservation of the type 2 calcium-ligating residues across the six domains of gelsolin suggests that this site exists in each of the domains. In total, gelsolin has the potential to bind eight calcium ions, two type 1 and six type 2. The function of the type 2 sites is to facilitate structural rearrangements within gelsolin as part of the activation and actin-binding and severing processes. We propose the novel type 2 site in G6 to be the critical site that initiates overall activation of gelsolin by releasing the tail latch that locks calcium-free gelsolin in a conformation unable to bind actin. 相似文献
45.
The role of post-translational modifications of the CXCR4 amino terminus in stromal-derived factor 1 alpha association and HIV-1 entry 总被引:8,自引:0,他引:8
Farzan M Babcock GJ Vasilieva N Wright PL Kiprilov E Mirzabekov T Choe H 《The Journal of biological chemistry》2002,277(33):29484-29489
The chemokine receptor CXCR4 plays critical roles in development, immune function, and human immunodeficiency virus type 1 (HIV-1) entry. Here we demonstrate that, like the CC-chemokine receptors CCR5 and CCR2b, CXCR4 is posttranslationally modified by sulfation of its amino-terminal tyrosines. The sulfate group at tyrosine 21 contributes substantially to the ability of CXCR4 to bind its ligand, stromal derived factor 1 alpha. Tyrosine sulfation plays a less significant role in CXCR4-dependent HIV-1 entry than in CCR5-dependent HIV-1 entry. In some cell lines, CXCR4 is efficiently modified by a chondroitin sulfate chain at serine 18, but neither HIV-1 entry nor stromal derived factor 1 alpha binding was affected by loss of this glycosaminoglycan. These data demonstrate a functional role for tyrosine sulfate in the CXC-chemokine receptor family and underscore a general difference in HIV-1 utilization of CCR5 and CXCR4. 相似文献
46.
The role of interleukin-4 (IL-4) in the inflammatory process has emerged recently. In this study, we investigated the effect of IL-4 on the angiogenic process in an in vitro experimental system. IL-4 significantly inhibited the proliferation of human umbilical vein endothelial cells (HUVEC) that was induced by the vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). VEGF- or bFGF-induced HUVEC chemotaxis was abrogated by the IL-4 treatment. In addition, the formation of tube-like structures by HUVEC in the presence of VEGF or bFGF was also severely down-regulated by IL-4. The inhibitory effects on the critical steps of angiogenesis were not observed with IL-6 that is abundantly found in the inflamed tissue. Our results suggest that IL-4 may play a regulatory role in normal physiology and provide the potential possibility for IL-4 as a therapeutic agent in the intervention of angiogenesis-related diseases. 相似文献
47.
48.
Ponnuraj K Bowden MG Davis S Gurusiddappa S Moore D Choe D Xu Y Hook M Narayana SV 《Cell》2003,115(2):217-228
Gram-positive pathogens such as staphylococci contain multiple cell wall-anchored proteins that serve as an interface between the microbe and its environment. Some of these proteins act as adhesins and mediate bacterial attachment to host tissues. SdrG is a cell wall-anchored adhesin from Staphylococcus epidermidis that binds to the Bbeta chain of human fibrinogen (Fg) and is necessary and sufficient for bacterial attachment to Fg-coated biomaterials. Here, we present the crystal structures of the ligand binding region of SdrG as an apoprotein and in complex with a synthetic peptide analogous to its binding site in Fg. Analysis of the crystal structures, along with mutational studies of both the protein and of the peptide, reveals that SdrG binds to its ligand with a dynamic "dock, lock, and latch" mechanism. We propose that this mechanism represents a general mode of ligand binding for structurally related cell wall-anchored proteins of gram-positive bacteria. 相似文献
49.
We have investigated the expression of neuropeptide Y (NPY) in C6 glioma cells after the glutamatergic stimulation by the in situ RT-PCR and immunocytochemical techniques. The expression of NPY mRNA correlated well with immunocytological findings in each series of experiments. NPY protein expression was enhanced by glutamate (1, 10, 50, 100 microM, and 1 mM) dose-dependently, and its expression was slightly increased by N-methyl-D-aspartate (NMDA; 1, 10, 100, 500 microM, and 1 mM) and kainic acid (1, 10, 100, 300 microM, and 1 mM). We pretreated the cells with dopamine, haloperidol, pentylenetetrazol, and muscimol before each stimulation. The pentylenetetrazol and muscimol did not significantly alter the patterns of NPY expression induced by the glutamatergic stimulation. On the other hand, the dopamine and haloperidol pretreatment significantly elevated the levels of NPY expression that were induced by NMDA and kainic acid. Our results indicate that NPY release is closely related to glutamatergic stimulation, and it could be dynamically mediated by GABAergic and dopaminergic costimulation. 相似文献
50.
Gray PC Greenwald J Blount AL Kunitake KS Donaldson CJ Choe S Vale W 《The Journal of biological chemistry》2000,275(5):3206-3212
Type II activin receptors (ActRII and ActRIIB) are single-transmembrane domain serine/threonine kinase receptors that bind activin to initiate the signaling and cellular responses triggered by this hormone. Inhibin also binds type II activin receptors and antagonizes many activin effects. Here we describe alanine scanning mutagenesis of the ActRII extracellular domain. We identify a cluster of three hydrophobic residues (Phe(42), Trp(60), and Phe(83)) that, when individually mutated to alanine in the context of the full-length receptor, cause the disruption of activin and inhibin binding to ActRII. Each of the alanine-substituted ActRII mutants retaining activin binding maintains the ability to form cross-linked complexes with activin and supports activin cross-linking to the type I activin receptor ALK4. Unlike wild-type ActRII, the three mutants unable to bind activin do not cause an increase in activin signaling when transiently expressed in a corticotroph cell line. Together, our results implicate these residues in forming a critical binding surface on ActRII required for functional interactions with both activin and inhibin. This first identification of a transforming growth factor-beta family member binding site may provide a general basis for characterizing binding sites for other members of the superfamily. 相似文献