Kumar PR, Yu Y, Sternglanz R, Johnston SA, Joshua-Tor L.
(2008)
NADP regulates the yeast GAL induction system.
Science,
319(5866), 1090-2, [19ID].
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| Transcriptional regulation of the galactose-metabolizing genes in Saccharomyces cerevisiae depends on three core proteins: Gal4p, the transcriptional activator that binds to upstream activating DNA sequences (UAS(GAL)); Gal80p, a repressor that binds to the carboxyl terminus of Gal4p and inhibits transcription; and Gal3p, a cytoplasmic transducer that, upon binding galactose and adenosine 5'-triphosphate, relieves Gal80p repression. The current model of induction relies on Gal3p sequestering Gal80p in the cytoplasm. However, the rapid induction of this system implies that there is a missing factor. Our structure of Gal80p in complex with a peptide from the carboxyl-terminal activation domain of Gal4p reveals the existence of a dinucleotide that mediates the interaction between the two. Biochemical and in vivo experiments suggests that nicotinamide adenine dinucleotide phosphate (NADP) plays a key role in the initial induction event.
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Nocek B, Mulligan R, Bargassa M, Collart F, Joachimiak A.
(2008)
Crystal structure of aminopeptidase N from human pathogen Neisseria meningitidis.
Protiens,
70 (1), 273-9, [SBC Staff 19ID].
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Qiu Y, Zhang R, Binkowski TA, Tereshko V, Joachimiak A, Kossiakoff A.
(2008)
The 1.38 A crystal structure of DmsD protein from Salmonella typhimurium, a proofreading chaperone on the Tat pathway.
Protiens,
Epub, ahead of print, [SBC Staff 19ID].
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| The DmsD protein is necessary for the biogenesis of dimethyl sulphoxide (DMSO) reductase in many prokaryotes. It performs a critical chaperone function initiated through its binding to the twin-arginine signal peptide of DmsA, the catalytic subunit of DMSO reductase. Upon binding to DmsD, DmsA is translocated to the periplasm via the so-called twin-arginine translocation (Tat) pathway. Here we report the 1.38 A crystal structure of the protein DmsD from Salmonella typhimurium and compare it with a close functional homolog, TorD. DmsD has an all-alpha fold structure with a notable helical extension located at its N-terminus with two solvent exposed hydrophobic residues. A major difference between DmsD and TorD is that TorD structure is a domain-swapped dimer, while DmsD exists as a monomer. Nevertheless, these two proteins have a number of common features suggesting they function by using similar mechanisms. A possible signal peptide-binding site is proposed based on structural similarities. Computational analysis was used to identify a potential GTP binding pocket on similar surfaces of DmsD and TorD structures. Proteins 2008. Published 2007 Wiley-Liss, Inc. |
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Cai-Guang Yang, Chengqi Yi, Erica M. Duguid, Christopher T. Sullivan, Xing Jian, Phoebe A. Rice & Chuan He
(2008)
Crystal structures of DNA/RNA repair enzymes AlkB and ABH2 bound to dsDNA
Nature,
452, 961-965 , [19BM].
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| Escherichia coli AlkB and its human homologues ABH2 and ABH3 repair DNA/RNA base lesions by using a direct oxidative dealkylation mechanism. ABH2 has the primary role of guarding mammalian genomes against 1-meA damage by repairing this lesion in double-stranded DNA (dsDNA), whereas AlkB and ABH3 preferentially repair single-stranded DNA (ssDNA) lesions and can repair damaged bases in RNA. Here we show the first crystal structures of AlkB–dsDNA and ABH2–dsDNA complexes, stabilized by a chemical cross-linking strategy. This study reveals that AlkB uses an unprecedented base-flipping mechanism to access the damaged base: it squeezes together the two bases flanking the flipped-out one to maintain the base stack, explaining the preference of AlkB for repairing ssDNA lesions over dsDNA ones. In addition, the first crystal structure of ABH2, presented here, provides a structural basis for designing inhibitors of this human DNA repair protein. |
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Tan K, Duquette M, Liu JH, Shanmugasundaram K, Joachimiak A, Gallagher JT, Rigby AC, Wang JH, Lawler J.
(2008)
Heparin-induced cis- and trans- dimerization modes of the thrombospondin-1 N-terminal domain.
J. Biol. Chem.,
283 (7), 3932-41, [19ID].
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| Through its interactions with proteins and proteoglycans, thrombospondin-1 (TSP-1) functions at the interface of the cell membrane and the extracellular matrix to regulate matrix structure and cellular phenotype. We have previously determined the structure of the high affinity heparin-binding domain of TSP-1, designated TSPN-1, in association with the synthetic heparin, Arixtra. To establish that the binding of TSPN-1 to Arixtra is representative of the association with naturally occurring heparins, we have determined the structures of TSPN-1 in complex with heparin oligosaccharides containing eight (dp8) and ten (dp10) subunits, by X-ray crystallography. We have found that (1) dp8 and dp10 bind to TSPN-1 in a manner similar to Arixtra, and (2) dp8 and dp10 induce the formation of trans and cis TSPN-1 dimers, respectively. In silico docking calculations partnered with our crystal structures support the importance of arginine residues in positions 29, 42 and 77 in binding sulfate groups of the dp8 and dp10 forms of heparin. The ability of several TSPN-1 domains to bind to glycosaminoglycans simultaneously probably increases the affinity of binding through multivalent interactions. The formation of cis and trans dimers of the TSPN-1 domain with relatively short segments of heparin further enhance the ability of TSP-1 to participate in high affinity binding to glycosaminoglycans. Dimer formation may also involve TSPN-1 domains from two separate TSP-1 molecules. This association would enable glycosaminoglycans to cluster TSP-1. |
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Found 801 results
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