2b7x
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(New page: 200px<br /><applet load="2b7x" size="450" color="white" frame="true" align="right" spinBox="true" caption="2b7x, resolution 3.0Å" /> '''Sequential reorganiza...)
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Revision as of 06:30, 21 November 2007
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Sequential reorganization of beta-sheet topology by insertion of a single strand
Overview
Insertions, duplications, and deletions of sequence segments are thought, to be major evolutionary mechanisms that increase the structural and, functional diversity of proteins. Alternative splicing, for example, is an, intracellular editing mechanism that is thought to generate isoforms for, 30%-50% of all human genes. Whereas the inserted sequences usually display, only minor structural rearrangements at the insertion site, recent, observations indicate that they may also cause more dramatic structural, displacements of adjacent structures. In the present study we test how, artificially inserted sequences change the structure of the beta-sheet, region in T4 lysozyme. Copies of two different beta-strands were inserted, into two different loops of the beta-sheet, and the structures were, determined. Not surprisingly, one insert "loops out" at its insertion site, and forms a new small beta-hairpin structure. Unexpectedly, however, the, second insertion leads to displacement of adjacent strands and a, sequential reorganization of the beta-sheet topology. Even though the, insertions were performed at two different sites, looping out occurred at, the C-terminal end of the same beta-strand. Reasons as to why a non-native, sequence would be recruited to replace that which occurs in the native, protein are discussed. Our results illustrate how sequence insertions can, facilitate protein evolution through both local and nonlocal changes in, structure.
About this Structure
2B7X is a Single protein structure of sequence from Bacteriophage t4 with SO4 as ligand. Active as Lysozyme, with EC number 3.2.1.17 Full crystallographic information is available from OCA.
Reference
Sequential reorganization of beta-sheet topology by insertion of a single strand., Sagermann M, Baase WA, Matthews BW, Protein Sci. 2006 May;15(5):1085-92. Epub 2006 Apr 5. PMID:16597830
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