1ezg
CRYSTAL STRUCTURE OF ANTIFREEZE PROTEIN FROM THE BEETLE, TENEBRIO MOLITOR
Structural highlights
FunctionANPY1_TENMO Contributes to protect body fluid from freezing at subzero temperatures. Lowers the freezing point of the hemolymph by about 2.5 degrees at a concentration of 1 mg/ml. Binds to nascent ice crystals and prevents further growth.[1] [2] [3] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedInsect antifreeze proteins (AFP) are much more effective than fish AFPs at depressing solution freezing points by ice-growth inhibition. AFP from the beetle Tenebrio molitor is a small protein (8.4 kDa) composed of tandem 12-residue repeats (TCTxSxxCxxAx). Here we report its 1.4-A resolution crystal structure, showing that this repetitive sequence translates into an exceptionally regular beta-helix. Not only are the 12-amino-acid loops almost identical in the backbone, but also the conserved side chains are positioned in essentially identical orientations, making this AFP perhaps the most regular protein structure yet observed. The protein has almost no hydrophobic core but is stabilized by numerous disulphide and hydrogen bonds. On the conserved side of the protein, threonine-cysteine-threonine motifs are arrayed to form a flat beta-sheet, the putative ice-binding surface. The threonine side chains have exactly the same rotameric conformation and the spacing between OH groups is a near-perfect match to the ice lattice. Together with tightly bound co-planar external water, three ranks of oxygen atoms form a two-dimensional array, mimicking an ice section. Mimicry of ice structure by surface hydroxyls and water of a beta-helix antifreeze protein.,Liou YC, Tocilj A, Davies PL, Jia Z Nature. 2000 Jul 20;406(6793):322-4. PMID:10917536[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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