A HAIRPIN-LOOP CONFORMATION IN TANDEM REPEAT SEQUENCE OF THE ICE NUCLEATION PROTEIN REVEALED BY NMR-SPECTROSCOPY

The H-1-NMR spectrum of a synthetic 24-residue peptide -G-V-D-S-S-L-I- A-G-Y-G-S-T-Q-T-S-G-S-D-S-A-L-T-24; INP24), comprising three repeats o f the 8-residue consensus sequence of Pseudomonas syringae ice nucleat ion protein, was fully assigned using 2-dimensional (2D) NMR spectrosc opy at 4 degrees C and 30 degrees C. Close proximity of the aliphatic protons between Leu(7), ILe(8), Ala(9), and the ring-protons of Tyr(11 ) was indicated from the observation of the inter-molecular nuclear Ov erhauser enhancement (NOE) effect. Hydrogen-bonding was strongly sugge sted for the NH group of Leu(7) from its extremely low-temperature coe fficient estimated from the temperature dependence of the chemical shi ft. These results indicate the formation of a hairpin-loop conformatio n constructed by a hexapeptide segment of INP24, -Leu(7)-Ile(8)-Ala(9) -Gly(10)-Tyr(11)-Gly(12). (C) 1997 Federation of European Biochemical Societies.