A review of multi-domain and flexible molecular chaperones studies by small-angle X-ray scattering

Abstract

Intrinsic flexibility is closely related to protein function, and a plethora of important regulatory proteins have been found to be flexible, multi-domain or even intrinsically disordered. On the one hand, understanding such systems depends on how these proteins behave in solution. On the other, small-angle X-ray scattering (SAXS) is a technique that fulfills the requirements to study protein structure and dynamics relatively quickly with few experimental limitations. Molecular chaperones from Hsp70 and Hsp90 families are multi-domain proteins containing flexible and/or disordered regions that play central roles in cellular proteostasis. Here, we review the structure and function of these proteins by SAXS. Our general approach includes the use of SAXS data to determine size and shape parameters, as well as protein shape reconstruction and their validation by using accessory biophysical tools. Some remarkable examples are presented that exemplify the potential of the SAXS technique. Protein structure can be determined in solution even at limiting protein concentrations (for example, human mortalin, a mitochondrial Hsp70 chaperone). The protein organization, flexibility and function (for example, the J-protein co-chaperones), oligomeric status, domain organization, and flexibility (for the Hsp90 chaperone and the Hip and Hep1 co-chaperones) may also be determined. Lastly, the shape, structural conservation, and protein dynamics (for the Hsp90 chaperone and both p23 and Aha1 co-chaperones) may be studied by SAXS. We believe this review will enhance the application of the SAXS technique to the study of the molecular chaperones.

Exploring intrinsically disordered proteins in Chlamydomonas reinhardtii

“…Moreover, as reported in the literature, IDPs found in plants are associated with many stress-response processes, acting as protein chaperones 56 or protecting other cellular components 2 . We have identified 20 IDPs related to unfolded protein binding or chaperone-function, with some illustrative examples, Hsp33 57 – 60 , Hsp70 and Hsp90 61 , belonging to the family of heat-shock proteins. Hsp70 and Hsp90 were also found in the Chlamydomonas phosphoproteome 14 indicating that they are phosphorylated.…”

A staphylococcal anti-sigma factor possesses a single-domain, carries different denaturant-sensitive regions and unfolds via two intermediates

“…Multi-domain proteins usually use their different domains to perform different functions [ 41 , 42 ]. Conversely, single-domain proteins most times use their different/overlapping regions or motifs to fulfilldifferent objectives [ 31 , 43 ].…”

A review and summary of the contents of biophysical reviews volume 8, 2016

“…These methods can sense the changes in protein solvation. Borges et al (2016): Small angle X-ray scattering (SAXS) enables biophysicists to study protein domains. The authors reviewed the use of SAXS for studying molecular structure of chaperones (Hsp70 and Hsp90).…”