The global structure dynamics of protein, such as domain reorientation motions, should have essential functional roles. However, they are rather hard to elucidate, particularly for sizeable proteins (typically, over 50 kDa). Because the type of analysis needs to quantify the large amplitude structural changes of protein, which is less achievable by NMR. The RDCs allow the type of analyses, but they are hard to measure for large proteins: the anti-TROSY or HSQC signals under the weakly aligning conditions become severely broadened to disable the RDC measurements. We have devised a TROSY-based approach for getting the alignment tensor (DIORITE) to overcome the limitation in the analysis using the RDCs for getting the global structural change of proteins (1, 2). Our approach uses only TROSY spectral changes induced by the alignment; therefore, it takes a full advantage of the TROSY signal narrowing effect in collecting the data for the protein in a weakly aligned state. This facilitates the analyses of the large amplitude motion of protein with less molecular size limitation relative to the RDC experiments.
The small-angle X-ray scattering (SAXS) gives complementary structure information to the alignment tensor by NMR. The combined use of DIORITE with SAXS has improved the accuracy for the analyses of the global structure changes of proteins.
In this presentation, I will describe the technical details in DIORITE, as an alternative to the RDCs, with its applications to the global structural change of various types of proteins in combined use of SAXS (3).