The conformational stability of ribosomal proteins L7 and L12 from E. coli. I. Circular dichroism study of the changes induced by ionic strength and solvents
✍ Scribed by Miloslav Boublik; Nathan Brot; Herbert Weissbach
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1973
- Tongue
- English
- Weight
- 518 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
Ribosomal proteins L~7~ and L~12~ are the only acidic proteins found on the 50S ribosomal subunit of Escherichia coli. The effect of ionic strength, helix‐promoting solvents and denaturating agents on the conformation of these proteins has been studied. It has been established that the helicity of L~7~ and L~12~ proteins (approx. 45–50% α helix) can be increased to 60–70% when they are exposed to helix‐promoting solvents such as methanol or ethanol in the presence of 0.1__M__ salt. High ionic strength by itself was without any effect on the conformation of the proteins. However, the solvent, 2,2,2‐trifluoroethanol increased the content of α helices up to 80% even in the absence of salt. Denaturating agents like urea (6__M__) or guanidine HCl (6__M__), decreased the content of the ordered structure below 20%. All conformational changes induced by salt or solvents were completely reversible and characterized by a broad transition showing a low degree of cooperativity. This might indicate the presence of discrete segments with variations in amino acid sequences and ordered structures with different stabilities.