biostudies-literatureBanks AOffice of Biological and Environmental Research of the U.S. Department of EnergyScientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of EnergyNational Institutes of HealthNIGMS NIH HHS1067-1079https://www.ebi.ac.uk/biostudies/studies/S-EPMC5883552biostudies-literatureUnknown114(5)Conformational malleability allows intrinsically disordered proteins (IDPs) to respond agilely to their environments, such as nonspecifically interacting with in vivo bystander macromolecules (or crowders). Previous studies have emphasized conformational compaction of IDPs due to steric repulsion by macromolecular crowders, but effects of soft attraction are largely unexplored. Here we studied the conformational ensembles of the IDP FlgM in both polymer and protein crowders by small-angle neutron scattering. As crowder concentrations increased, the mean radius of gyration of FlgM first decreased but then exhibited an uptick. Ensemble optimization modeling indicated that FlgM conformations under protein crowding segregated into two distinct populations, one compacted and one extended. Coarse-grained simulations showed that compacted conformers fit into an interstitial void and occasionally bind to a surrounding crowder, whereas extended conformers snake through interstitial crevices and bind multiple crowders simultaneously. Crowder-induced conformational segregation may facilitate various cellular functions of IDPs.Biophysical journalIntrinsically Disordered Protein Exhibits Both Compaction and Expansion under Macromolecular Crowding.PMC5883552R01 GM088187R35 GM118091GM118091GM088187Zhou HXWeiss KLBanks AStanley CBQin SfalseIntrinsically Disordered Protein Exhibits Both Compaction and Expansion under Macromolecular Crowding.Conformational malleability allows intrinsically disordered proteins (IDPs) to respond agilely to their environments, such as nonspecifically interacting with in vivo bystander macromolecules (or crowders). Previous studies have emphasized conformational compaction of IDPs due to steric repulsion by macromolecular crowders, but effects of soft attraction are largely unexplored. Here we studied the conformational ensembles of the IDP FlgM in both polymer and protein crowders by small-angle neutron scattering. As crowder concentrations increased, the mean radius of gyration of FlgM first decreased but then exhibited an uptick. Ensemble optimization modeling indicated that FlgM conformations under protein crowding segregated into two distinct populations, one compacted and one extended. Coarse-grained simulations showed that compacted conformers fit into an interstitial void and occasionally bind to a surrounding crowder, whereas extended conformers snake through interstitial crevices and bind multiple crowders simultaneously. Crowder-induced conformational segregation may facilitate various cellular functions of IDPs.2018-01-01T00:00:00Z2018 Mar2025-04-04T19:33:53.296Z2025-04-04T19:33:53.296ZS-EPMC58835522953939410.1016/j.bpj.2018.01.011