1xrk
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(New page: 200px<br /><applet load="1xrk" size="450" color="white" frame="true" align="right" spinBox="true" caption="1xrk, resolution 1.50Å" /> '''Crystal structure of...)
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Revision as of 04:10, 21 November 2007
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Crystal structure of a mutant bleomycin binding protein from Streptoalloteichus hindustanus displaying increased thermostability
Overview
Limited thermostability of antibiotic resistance markers has restricted, genetic research in the field of extremely thermophilic Archaea and, bacteria. In this study, we used directed evolution and selection in the, thermophilic bacterium Thermus thermophilus HB27 to find thermostable, variants of a bleomycin-binding protein from the mesophilic bacterium, Streptoalloteichus hindustanus. In a single selection round, we identified, eight clones bearing five types of double mutated genes that provided T., thermophilus transformants with bleomycin resistance at 77 degrees C, while the wild-type gene could only do so up to 65 degrees C. Only six, different amino acid positions were altered, three of which were glycine, residues. All variant proteins were produced in Escherichia coli and, analyzed biochemically for thermal stability and functionality at high, temperature. A synthetic mutant resistance gene with low GC content was, designed that combined four substitutions. The encoded protein showed up, to 17 degrees C increased thermostability and unfolded at 85 degrees C in, the absence of bleomycin, whereas in its presence the protein unfolded at, 100 degrees C. Despite these highly thermophilic properties, this mutant, was still able to function normally at mesophilic temperatures in vivo., The mutant protein was co-crystallized with bleomycin, and the structure, of the binary complex was determined to a resolution of 1.5 A. Detailed, structural analysis revealed possible molecular mechanisms of, thermostabilization and enhanced antibiotic binding, which included the, introduction of an intersubunit hydrogen bond network, improved, hydrophobic packing of surface indentations, reduction of loop, flexibility, and alpha-helix stabilization. The potential applicability of, the thermostable selection marker is discussed.
About this Structure
1XRK is a Single protein structure of sequence from Streptoalloteichus hindustanus with SO4 and BLM as ligands. Full crystallographic information is available from OCA.
Reference
Engineering a selectable marker for hyperthermophiles., Brouns SJ, Wu H, Akerboom J, Turnbull AP, de Vos WM, van der Oost J, J Biol Chem. 2005 Mar 25;280(12):11422-31. Epub 2005 Jan 7. PMID:15640151
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