Structure of the N-terminus of the Escherichia coli ribosomal protein L7/L12

Three mutant forms of the ribosomal protein L7/L12 (S1Y, M14Y and M26Y) were constructed in order to use the Tyr residues as internal labels at the N-terminal region. The proteins were studied by the methods of 1H-NMR, Fluorescence, Circular dichroism spectroscopy and Differencial scanning calorimetry. The secondary structure of N-terminus (residues 1-36) was predicted by the programme "Globule" [1, 2]. Y1 is located in a structurally disordered region at the free end of the molecule. M14 and M26 are located in structurally ordered regions. The replacement M14 does not change the structure of the protein. The replacement M26 disturbs the helicity in the region of the mutation. The first 1-5 positions from the N-terminus of L7/L12 are disordered, the position 7-14 participate in an alpha-helical/beta-structural region and position 19-30 in a strongly alpha-helical region.