title: Study of tyrosine-containing mutants of ribosomal protein L7/L12 from Escherichia coli.
abstract: Three mutant forms of the ribosomal protein L7/L12 with replacements of Ser1, 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.
authors.affiliation: Institute of Biophysics, BAS, Sofia, Bulgaria.
authors.forename: R T
authors.initials: RT
authors.lastname: Todorova
authors.forename: V V
authors.initials: VV
authors.lastname: Rogov
authors.forename: K S
authors.initials: KS
authors.lastname: Vasilenko
authors.forename: E A
authors.initials: EA
authors.lastname: Permyakov
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D003956:Dialysis; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009154:Mutation / Q000502:physiology*; D010649:Phenylalanine / Q000378:metabolism; D011489:Protein Denaturation; D012269:Ribosomal Proteins / Q000235:genetics* / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014443:Tyrosine / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012269:Ribosomal Proteins; D014443:Tyrosine; D010649:Phenylalanine