ISSN:
1615-6102
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Small angle X-ray scattering measurements and electron microscopic studies were carried out onE. coli phosphofructokinase (E.C. 2.7.1.11; ATP: D-fructose-6-phosphate-1-phosphotransferase). The results suggest a tetrahedral arrangement of the protomers resulting in a radius of gyration of the enzyme of R=34.6 Å and a Stokes' radius of R0=44.0 Å. The stereochemical arrangement of the four protomers, each of a molecular weight of 35,000, within theE. coli enzyme was further substantiated by a comparison of theoretical scattering functions with the experimental scattering measurements in dilute solutions of phosphofructokinase under physiological conditions. Moreover, from other hydrodynamic measurements,e.g., intrinsic viscosity and sedimentation coefficient, theMandelkern-Scheraga factor, β, was calculated to be 2,095×106, which is significantly lower than the β0 for rigid spheres of 2,112×106. This low β-value might be due to a considerable porosity of the four protomers for mobile water molecules. The β-value of 2,095×106 is an indication of a porous sphere of almost uniform density at aDebye shielding ratio of 6.5, corresponding to a sphere radius of 22.0 Å for one protomer and an inverse hydrodynamic shielding length of 0.45 Å−1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01280199
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