The asymmetric unit comprises two RiAFP molecules juxtaposed with their ice-binding surfaces, however the protein is monomer in the solutio
Overall Structure
The crystallographic structure of RiAFP was defined recently[1]. It reveals a new β-solenoid architecture that forms β-sandwich of two parallel 6 and 7 stranded-sheets of remarkable regularity. The β-sheets lie on top of each other with the upper and lower strands parallel but in the opposite orientation. Two ends deviate from β helix regularity by forming capping structures. These capping structures help to prevent end-to-end associations that would spoil the solubility of RiAFP and lead to oligomerization and aggregation.
The three residues in β-strand 11 at the C terminus (Gln110, Gln112, and Ile114) that are too bulky to be accommodated into the core may also contribute to the capping structure to prevent amyloid-like polymerization. RiAFP solenoid possesses compressed nature. In the core of RiAFP, the side chains within apposed β-strands from the two β-sheets are staggered, allowing the side chains to interdigitate and pack tightly against one another. Most of the side chains in the core are from Ala, Ser and Thr. Those residues create a more compact fold that may contribute to the high stability and antifreeze activity of RiAFP. Within the core there are hydrogen bonds between Thr-Ser (65-55, 85-75, 132-124 respectively) and one disulfide bond between Cys4-Cys21, that contributes to stabilization of the whole structure. The β-turns in the structure contain mostly Gly or Pro residues.
Ice Binding Surface (IBS)
Function
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chain A without His-Tag
Disease
Relevance
Structural highlights
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- ↑ Hakim A, Nguyen JB, Basu K, Zhu DF, Thakral D, Davies PL, Isaacs FJ, Modis Y, Meng W. Crystal structure of an insect antifreeze protein and its implications for ice binding. J Biol Chem. 2013 Apr 26;288(17):12295-304. doi: 10.1074/jbc.M113.450973. Epub, 2013 Mar 12. PMID:23486477 doi:10.1074/jbc.M113.450973