title: A circular loop of the 16-residue repeating unit in ice nucleation protein.
abstract: Ice nucleation protein (INP) from Gram-negative bacteria promotes the freezing of supercooled water. The central domain of INPs with 1034-1567 residues consists of 58-81 tandem repeats with the 16-residue consensus sequence of AxxxSxLTAGYGSTxT. This highly repetitive domain can also be represented by tandem repeats of 8-residues or 48-residues. In order to elucidate the structure of the tandem repeats, NMR measurements were made for three synthetic peptides including QTARKGSDLTTGYGSTS corresponding to a section of the repetitive domains in Xanthomonas campestris INP. One remarkable observation is a long-range NOE between the side chains of Tyr(i) and Ala(i-10) in the 17-residue peptide. Medium-range NOEs between the side chains of Tyr(i) and Leu(i-4), Thr(i-3) or Thr(i-2) were also observed. These side chain-side chain interactions can be ascribed to CH/pi interaction. Structure calculation reveals that the 17-residue peptide forms a circular loop incorporating the 11-residue segment ARKGSDLTTGY.
authors: High-Resolution NMR Laboratory, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors: Yasuhiro
authors: Y
authors: Kumaki
authors: Keiichi
authors: K
authors: Kawano
authors: Kunio
authors: K
authors: Hikichi
authors: Takeshi
authors: T
authors: Matsumoto
authors: Norio
authors: N
authors: Matsushima
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D016384:Consensus Sequence; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D016959:Xanthomonas campestris
chemical_list: D001425:Bacterial Outer Membrane Proteins; D010455:Peptides; C063113:ice nucleation protein