Physical studies on the ribosomal protein S2 from the Escherichia coli 30S subunit

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Abstract
The protein S2 was isolated from the 30S subunit of E. coli A19 ribosomes. This salt-extracted protein is soluble and does not aggregate at salt concentrations of 0.3-0.4 M as used under reconstitution conditions. This differs from the S2 protein extracted by the acetic acid and urea method. The MW from sedimentation equilibrium was 29,200 and the protein had a .**GRAPHIC**. value of 2.36 S. The apparent specific volume at 20.degree. C was 0.726 ml .cntdot. g-1, and the .**GRAPHIC**. was 7.37 .times. 10-7 cm2 s-1. The value for intrinsic viscosity was found to be 6.42 ml .cntdot. g-1. An axial ratio of (5-6):1 for a prolate ellipsoid of revolution was estimated by using these parameters. The circular dichroism and PMR studies show that protein S2 has both substantial amounts of .alpha. helix and .beta.-pleated sheet in solution and appears as a folded protein and not a random coil structure.