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A Ca2+ dependent bacterial antifreeze protein domain has a novel beta-helical ice-binding fold
Citation
Garnham, CP and Gilbert, JA and Hartman, CP and Campbell, RL and Laybourn-Parry, J and Davis, PL, A Ca2+ dependent bacterial antifreeze protein domain has a novel beta-helical ice-binding fold, Biochemical Journal, 411, (1) pp. 171-180. ISSN 0264-6021 (2008) [Refereed Article]
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Official URL: http://www.biochemj.org/bj/default.htm
Abstract
AFPs (antifreeze proteins) are produced by many organisms
that inhabit ice-laden environments. They facilitate survival
at sub-zero temperatures by binding to, and inhibiting, the
growth of ice crystals in solution. The Antarctic bacterium
Marinomonas primoryensis produces an exceptionally large
(>1 MDa) hyperactive Ca2+-dependent AFP. We have cloned,
expressed and characterized a 322-amino-acid region of the
protein where the antifreeze activity is localized that shows
similarity to the RTX (repeats-in-toxin) family of proteins. The
recombinant protein requires Ca2+ for structure and activity, and it
is capable of depressing the freezing point of a solution in excess
of 2°C at a concentration of 0.5 mg/ml, therefore classifying it
as a hyperactive AFP. We have developed a homology-guided
model of the antifreeze region based partly on the Ca2+-bound β-
roll from alkaline protease. The model has identified both a novel
β-helical fold and an ice-binding site. The interior of the !-helix
contains a single row of bound Ca2+ ions down one side of the
structure and a hydrophobic core down the opposite side. The icebinding
surface consists of parallel repetitive arrays of threonine
and aspartic acid/asparagine residues located down the Ca2+-
bound side of the structure. The model was tested and validated
by site-directed mutagenesis. It explains the Ca2+-dependency of
the region, as well its hyperactive antifreeze activity. This is the
first bacterial AFP to be structurally characterized and is one of
only five hyperactive AFPs identified to date.
Item Details
| Item Type: | Refereed Article |
|---|---|
| Keywords: | Antarctic bacterium, antifreeze protein, calcium binding, b-helix, Marinomonas primoryensis, repeats-in-toxin proteins, RTX proteins |
| Research Division: | Biological Sciences |
| Research Group: | Microbiology |
| Research Field: | Microbial ecology |
| Objective Division: | Environmental Management |
| Objective Group: | Management of Antarctic and Southern Ocean environments |
| Objective Field: | Biodiversity in Antarctic and Southern Ocean environments |
| UTAS Author: | Laybourn-Parry, J (Professor Johanna Laybourn-Parry) |
| ID Code: | 53340 |
| Year Published: | 2008 |
| Web of Science® Times Cited: | 88 |
| Deposited By: | Research Division |
| Deposited On: | 2008-11-29 |
| Last Modified: | 2012-11-13 |
| Downloads: | 433 View Download Statistics |
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