2af5: Difference between revisions

[[Image:2af5.gif|left|200px]]<br /><applet load="2af5" size="350" color="white" frame="true" align="right" spinBox="true"  

Although the beta-rich self-assemblies are a major structural class for polypeptides and the focus of intense research, little is known about their atomic structures and dynamics due to their insoluble and noncrystalline nature. We developed a protein engineering strategy that captures a self-assembly segment in a water-soluble molecule. A predefined number of self-assembling peptide units are linked, and the beta-sheet ends are capped to prevent aggregation, which yields a mono-dispersed soluble protein. We tested this strategy by using Borrelia outer surface protein (OspA) whose single-layer beta-sheet located between two globular domains consists of two beta-hairpin units and thus can be considered as a prototype of self-assembly. We constructed self-assembly mimics of different sizes and determined their atomic structures using x-ray crystallography and NMR spectroscopy. Highly regular beta-sheet geometries were maintained in these structures, and peptide units had a nearly identical conformation, supporting the concept that a peptide in the regular beta-geometry is primed for self-assembly. However, we found small but significant differences in the relative orientation between adjacent peptide units in terms of beta-sheet twist and bend, suggesting their inherent flexibility. Modeling shows how this conformational diversity, when propagated over a large number of peptide units, can lead to a substantial degree of nanoscale polymorphism of self-assemblies.

2AF5 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Borrelia_burgdorferi Borrelia burgdorferi]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2AF5 OCA].  

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