[Secondary structure of binase in solution by 1H NMR]

Nearly all resonances were assigned in the two-dimensional 1H NMR spectra of binase, guanylospecific ribonuclease from Bacillus intermedius containing 109 amino acid residues. The exchange rates of amide protons with the solvent deuterium were measured in 2H2O at pH 6.7 and 30 degrees C. Coupling constants 3J of H-NC alpha-H, NOE contacts, solvent exchange rates of amide protons, and indices of C alpha H chemical shifts were measured, and the binase secondary structure was deduced from these data. It involves three alpha-helices in the N-terminal part (the 6-16, 26-31, and 41-45 segments) and a beta-sheet formed by five antiparallel beta-strands (51-55, 71-75, 86-90, 95-99, and 104-108 segments). The binase secondary structure was compared with that of its closest homologue, barnase from B. amyloliquefaciens.