Dynamics of antifreeze glycoproteins in the presence of ice.
Antifreeze glycoproteins from the Greenland cod Boreogadus saida were dimethylated at the N-terminus (m*AFGP) and their dynamics and conformational properties were studied in the presence of ice using (13)C-NMR and FTIR spectroscopy. (13)C-NMR experiments of m*AFGP in D(2)O, in H(2)O, and of freeze-dried m*AFGP were performed as a function of temperature. Dynamic parameters ((1)H T(1 rho) and T(CH)) obtained by varying the contact time revealed notable differences in the motional properties of AFGP between the different states. AFGP/ice dynamics was dominated by fast-scale motions (nanosecond to picosecond time scale), suggesting that the relaxation is markedly affected by the protein hydration. The data suggest that AFGP adopts a similar type of three-dimensional fold both in the presence of ice and in the freeze-dried state. FTIR studies of the amide I band did not show a single prevailing secondary structure in the frozen state. The high number of conformers suggests a high flexibility, and possibly reflects the necessity to expose more ice-binding groups. The data suggest that the effect of hydration on the local mobility of AFGP and the lack of significant change in the backbone conformation in the frozen state may play a role in inhibiting the ice crystal growth.
Tsvetkova
Nelly M
NM
Section of Molecular and Cellular Biology, University of California, Davis, California 95616, USA. nmsvetkova@ucdavis.edu
Phillips
Brian L
BL
Krishnan
Viswanathan V
VV
Feeney
Robert E
RE
Fink
William H
WH
Crowe
John H
JH
Risbud
Subhash H
SH
Tablin
Fern
F
Yeh
Yin
Y
D000818:Animals; D021301:Antifreeze Proteins / Q000737:chemistry*; D005399:Fishes; D007053:Ice; D009682:Magnetic Resonance Spectroscopy; D011312:Pressure; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared
D021301:Antifreeze Proteins; D007053:Ice