Solid-state NMR on a type III antifreeze protein in the presence of ice.
Antifreeze proteins (AFPs) are found in fish, insects, plants, and a variety of other organisms where they serve to prevent the growth of ice at subzero temperatures. Type III AFPs cloned from polar fishes have been studied extensively with X-ray crystallography, liquid-state NMR, and site directed mutagenesis and are, therefore, among the best characterized AFPs. A flat surface on the protein has previously been proposed to be the ice-binding site of type III AFP. The detailed nature of the ice binding remains controversial since it is not clear whether only polar or also hydrophobic residues are involved in ice binding and there is no structural information available of a type III AFP bound to ice. Here we present a high-resolution solid-state NMR study of a type III AFP (HPLC-12 isoform) in the presence of ice. The chemical-shift differences we detected between the frozen and the nonfrozen state agree well with the proposed ice-binding site. Furthermore, we found that the (1)H T(1) of HPLC-12 in frozen solution is very long compared to typical (1)H of proteins in the solid state as for example of ubiquitin in frozen solution.
Siemer
Ansgar B
AB
Department of Chemistry, MC3113, Columbia University, New York, New York 10027, USA. as3211@columbia.edu
McDermott
Ann E
AE
D000818:Animals; D021343:Antifreeze Proteins, Type III / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray / Q000379:methods; D005399:Fishes; D005615:Freezing; D057927:Hydrophobic and Hydrophilic Interactions; D007053:Ice; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008968:Molecular Conformation; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D013499:Surface Properties; D014867:Water / Q000737:chemistry
D021343:Antifreeze Proteins, Type III; D007053:Ice; D020033:Protein Isoforms; D014867:Water