Study of tyrosine-containing mutants of ribosomal protein [formula omitted] from Escherichia coli

• Published in: Biophysical chemistry 1996-11, Vol.62 (1), p.39-45
• Main Authors: Todorova, Roumiana T., Rogov, Vladimir V., Vasilenko, Kostia S., Permyakov, Eugene A.
• Format: Article
• Language: English
• Subjects: Circular dichroism; Fluorescent spectroscopy; Microcalorimetry; Mutant proteins [formula omitted]; pH-titration curves; Thermostability
• ISSN: 0301-4622; 1873-4200
• DOI: 10.1016/S0301-4622(96)02176-X

Three mutant forms of the ribosomal protein L7 L12 with replacements of Serl, Met14 and Met26 to Tyr were studied by the methods of fluorescence spectroscopy, circular dichroism and microcalorimetry. The amino-acid residue Tyr14 in the protein L7 L12 Tyr14 is located in a region with a more organized structure than Tyr26 in protein L7 L12 Tyr26. The replacements Ser1 → Tyr1 and Met14 → Tyr14 do not affect the secondary structure of protein L7 L12 . The replacement Met26 → Tyr26 stabilizes the secondary structure of protein L7 L12 . A pH-induced temperature transition was observed in the pH range 5.0–7.3 in protein L7 L12 Tyr14 by tyrosine fluorescence. Analogous transitions were observed for protein L7 L12 Tyr26 by Tyr fluorescence and for the wild type protein L7 L12 by Phe fluorescence. Three pH-dependent states of protein L7 L12 and its mutant forms L7 L12 Tyr1 and L7 L12 Tyr14 were found on the microcalorimetric melting curves. The characteristics of protein L7 L12 Tyr14 are very close to the wild type protein L7 L12 and it is a suitable object for studying the structure of the N-terminal part of molecule by two-dimentional 1H-NMR.