Effect of type III antifreeze protein dilution and mutation on the growth inhibition of ice

Mutation of residues at the ice-binding site of type III antifreeze protein (AFP) not only reduced antifreeze activity as indicated by the failure to halt ice crystal growth, but also altered ice crystal morphology to produce elongated hexagonal bipyramids. In general, the c axis to a axis ratio of...

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Bibliographic Details
Published in:Biophysical journal 1996-11, Vol.71 (5), p.2346-2355
Main Authors: DeLuca, C.I., Chao, H., Sönnichsen, F.D., Sykes, B.D., Davies, P.L.
Format: Article
Language:English
Subjects:
Animals
Antifreeze Proteins
Crystallography
Flounder
Freezing
Glycoproteins - chemistry
Glycoproteins - genetics
Ice
Magnetic Resonance Spectroscopy
Point Mutation
Recombinant Proteins
Structure-Activity Relationship
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Summary:Mutation of residues at the ice-binding site of type III antifreeze protein (AFP) not only reduced antifreeze activity as indicated by the failure to halt ice crystal growth, but also altered ice crystal morphology to produce elongated hexagonal bipyramids. In general, the c axis to a axis ratio of the ice crystal increased from approximately 2 to over 10 with the severity of the mutation. It also increased during ice crystal growth upon serial dilution of the wild-type AFP. This is in marked contrast to the behavior of the alpha-helical type I AFPs, where neither dilution nor mutation of ice-binding residues increases the c:a axial ratio of the ice crystal above the standard 3.3. We suggest that the ice crystal morphology produced by type III AFP and its mutants can be accounted for by the protein binding to the prism faces of ice and operating by step growth inhibition. In this model a decrease in the affinity of the AFP for ice leads to filling in of individual steps at the prism surfaces, causing the ice crystals to grow with a longer c:a axial ratio.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(96)79476-6