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Biophys J. 2001 Mar;80(3):1169-73.

Modeling Pseudomonas syringae ice-nucleation protein as a beta-helical protein.

Author information

1
Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada.

Abstract

Antifreeze proteins (AFPs) inhibit the growth of ice, whereas ice-nucleation proteins (INPs) promote its formation. Although the structures of several AFPs are known, the structure of INP has been modeled thus far because of the difficulty in determining membrane protein structures. Here, we present a novel model of an INP structure from Pseudomonas syringae based on comparison with two newly determined insect AFP structures. The results suggest that both this class of AFPs and INPs may have a similar beta-helical fold and that they could interact with water through the repetitive TXT motif. By theoretical arguments, we show that the distinguishing feature between an ice inhibitor and an ice nucleator lies in the size of the ice-interacting surface. For INPs, the larger surface area acts as a template that is larger than the critical ice embryo surface area required for growth. In contrast, AFPs are small enough so that they bind to ice and inhibit further growth without acting as a nucleator.

PMID:
11222281
PMCID:
PMC1301312
DOI:
10.1016/S0006-3495(01)76093-6
[Indexed for MEDLINE]
Free PMC Article

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