Figure 4

The GspL^fld dimer exhibits plasticity at the interface. (a) Schematic representation of the dimer of crystal form 1 viewed along the twofold axis (double headed arrow) and the dimer of crystal form 2 seen in the analogous way. Each block represents the whole ferredoxin-like domain and the depiction portrays this particular orientation of the dimer. The different proximity of interacting strands results in open (crystal form 1) and closed (crystal form 2) variant of the GspL^fld dimer. (b) The detailed view on the beta strands contributing to the interaction interfaces of crystal forms 1 and 2. The dramatically different inter-strand distances result in complementation of the interface with the extension of antiparallel β-sheet in case of crystal form 2 and lack of thereof in crystal form 1. The twofold axis is marked with a black diad symbol. The open variant of the crystal form 1 is mediated by coordination of a water molecule, indicated in dark red sphere. The two distinct scenarios can be fulfilled by the N-H of Leu327 and the C = O of Phe329′. The distances between main chains’ N and C = O groups are labeled with yellow dashed lines and reported in Å. The models are shown in the electron density 2Fo-Fc maps contoured at 2σ. (c) The plasticity of the GspL^fld reflected by interdomain tilting of 3°. (d) The dimer of crystal form 1 incorporated into the schematic representation of the GspL full-length dimer.