Abstract
Structure determination of multidomain proteins or protein–membrane complexes is one of the most challenging tasks in modern structural biology. High-resolution techniques, like NMR or X-ray crystallography, are limited to molecules of moderate size or those that can be crystallized easily. Both methods encounter serious technical obstacles in structural analysis of protein–membrane systems. This work describes an emerging biophysical technique that combines segmental isotope labeling of proteins with Fourier transform infrared (FTIR) spectroscopy, which provides site-specific structural information on proteins and allows structural characterization of protein–membrane complexes. Labeling of a segment of the protein with13C results in infrared spectral resolution of the labeled and unlabeled parts and thus allows identification of structural changes in specific domains/segments of the protein that accompany functional transitions. Segmental isotope labeling also allows determination of the precise configuration of protein–membrane complexes by polarized attenuated total reflection FTIR (ATR–FTIR) spectroscopy. These new developments offer solutions to functionally important site-specific structural changes in proteins and protein–membrane complexes that are hard to approach using conventional methods.
Highlights
Proteins often carry out their specific functions by forming complexes with other proteins, nucleic acids, membranes or other cell components
While the most valuable structural information on macromolecular complexes has been provided by atomic-resolution techniques such as X-ray crystallography and NMR, structural characterization of protein–membrane complexes is a challenging problem for both methods [3,6,8,10,11,15]
Conventional Fourier transform infrared (FTIR) spectroscopy is unable to distinguish between structural changes taking place in individual proteins in a complex or different domains of a protein during functional transitions
Summary
Proteins often carry out their specific functions by forming complexes with other proteins, nucleic acids, membranes or other cell components. There is an urgent need to develop new biophysical or other technologies to characterize the structure and dynamics of proteins in their membrane-bound state and to resolve structural changes occurring in specific domains or segments of the protein. Infrared spectroscopy is an inherently versatile biophysical tool for structural analysis of protein complexes [1,2,17]. This method is not limited to the molecular size and can provide structural information on all components of the system, e.g., proteins, lipids, nucleic acids, etc., without the need of labeling the molecules with spectroscopic probes. Polarized ATR–FTIR spectroscopy allows determination of the orientation of simple molecules, such as lipids, peptides, and proteins that have a rotational
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
