Article info Vol. 4  No. 1   pp.  18 ~ 24
Title Structure determination of biological macromolecular complexes by small-angle X-ray scattering (SAXS) combined with validating tools
Authors Donghyuk Shin, Seungsu Han and Sangho Lee*
Institutions Department of Biological Sciences, Sungkyunkwan University, Suwon 16419, Korea. *Correspondence: sangholee@skku.edu
Abstract The molecular world in a cell is operated by the action of biological macromolecular complexes in solution. The past couple of decades have witnessed an incredible advance in our understanding of atomic details of biological macromolecular complexes, mainly driven by X-ray crystallography. Despite the wealth of structural information, crystallographic structure determination of the biological complexes still remains challenging mostly because such complexes often resist to be crystallized. Small-angle X-ray scattering (SAXS) is emerging as an alternative to provide structural information for the biological macromolecular complexes at low resolution in solution. SAXS is advantageous in that it does not require crystalline state of the complexes and that multiple conformational states and/or conformational changes can be observed in solution. Combined with pre-existing high-resolution structures of components of the macromolecular complexes, SAXS can be used to build a testable molecular model for the complex. The structural model driven by the SAXS data can then be validated by biophysical, biochemical and cellular techniques. Here we attempt to review recent advances in application of SAXS to uncover the molecular basis of macromolecular complexes. Such a hybrid approach equipped with SAXS and complementary validation tools may be proven useful to obtain structural insights into the function of biological complexes when no high-resolution structure determination techniques such as crystallography, NMR and electron microscopy are applicable.