1. We have simultaneously collected composition-dependent static and dynamic light scattering data on mixtures of non-interacting and interacting proteins, and developed a global analysis of the composition-dependence of both quantities. Contrary to expectation, addition of dynamic light scattering data did not enhance the resolution of characterization obtainable using static light scattering data only. A preliminary description of this work was presented in last year's report, but analysis of the data has since been refined and extended, enabling a more detailed analysis of the relative information content of the two types of data. (B. Monterroso, CIB) 2. We have measured the dependence of the intensity of light scattering upon protein concentration in solutions of FtsZ containing either GTP an a GTP-regenerating system or GPCPP, a slowly hydrolyzable GTP analog, in the presence of varying concentrations of Mg++ ion. The simplest interpretation of the observed dependence is that self-association of either FtsZ-GTP or FtsZ-GPCPP proceeds initially by linear growtn according to an indefinite isodesmic scheme, followed by cooperative formation of a stable oligomer or narrow size distribution of oligomers of size 30-40 subunits that are thought to be cyclic. A preliminary description of this work was presented in last year's report. During the last year, the static light scattering results have been extended to include angular dependence, and results obtained from measurements of dynamic light scattering and sedimentation have enabled a significant refinement and extension of conclusions previously derived (G. Rivas, CIB).
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