To confirm the results of the rigid body modeling, the ensemble optimization method was chosen. This method randomly generates a large number of models of multidomain proteins using the rigid body approach. Then, using a genetic algorithm, the fraction of the models that create an ensemble with the best fit to the experimental data are selected. Unfortunately, the EOM method can be applied only to single-chain proteins, so it was possible to test only the monomeric form of the barley SGT1. The models of the barley SGT1 flexible structure were tested in two ways: by using structural models of all SGT1 domains, and by using models of only the TPR and CS domains. The rigid body analysis performed for the structural models of all domains agreed well with our experimental data. However, the possibility that the SGS domain has a dynamic character with a minor fraction of secondary structure cannot be excluded. A random pool of the SGT1 monomer models with the folded SGS domain is characterized by an average radius of gyration RG =3.67 nm, and a pool of models with the SGS domain represented as dummy residues is characterized by a RG value of 4.10 nm. After minimization of the final ensemble, the histogram of RG values differs significantly from the histogram (-)-Tetramisole generated for the random starting pool. The model with the folded SGS domain is characterized by an average RG value of 5.08 nm. The model with the unfolded SGS domain is characterized by RG value of 5.39 nm which is Albaspidin-AA slightly higher than the RG value calculated directly from the experimental data using 1 M NaCl. In both the cases, bell-shaped RG histograms were observed, with an additional maximum just above 4 nm for the model with the folded SGS domain. On the basis of analysis of the RG histogram, we concluded that the barley SGT1 monomer has some degree of flexibility but has a limited range. It is known that the human SGT1 protein does not dimerize under the conditions in which the SGT1 proteins from Arabidopsis thaliana and Saccharomyces cerevisiae form dimers. A comparison of the amino acid sequences of SGT1 proteins from various species has shown that the region of plant SGT1 that contains charged or polar residues participates in dimer interface formation.