Hyperactive antifreeze protein from an Antarctic sea ice bacterium Colwellia sp. has a compound ice‐binding site without repetitive sequences. (4th July 2014)

• Record Type: Journal Article
• Authors: Hanada, Yuichi; Nishimiya, Yoshiyuki; Miura, Ai; Tsuda, Sakae; Kondo, Hidemasa
• Is Part Of: FEBS journal. Volume 281:Number 16(2014)
• Page Start: 3576
• Page End: 3590
• Publication Date: 2014-07-04
• Subjects: Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.12878
• Languages: English
• ISSNs: 1742-464X

Abstract

<abstract abstract-type="main" id="febs12878-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="febs12878-sec-0001" sec-type="section"> <p>Antifreeze proteins (AFPs) are structurally diverse macromolecules that bind to ice crystals and inhibit their growth to protect the organism from injuries caused by freezing. An AFP identified from the Antarctic bacterium <italic>Colwellia</italic> sp. strain SLW05 (<italic>Col</italic>AFP) is homologous to AFPs from a wide variety of psychrophilic microorganisms. To understand the antifreeze function of <italic>Col</italic>AFP, we have characterized its antifreeze activity and determined the crystal structure of this protein. The recombinant <italic>Col</italic>AFP exhibited thermal hysteresis activity of approximately 4 °C at a concentration of 0.14 m<sc>m</sc>, and induced rapid growth of ice crystals in the hexagonal direction. Fluorescence‐based ice plane affinity analysis showed that <italic>Col</italic>AFP binds to multiple planes of ice, including the basal plane. These observations show that <italic>Col</italic>AFP is a hyperactive AFP. The crystal structure of <italic>Col</italic>AFP determined at 1.6 Å resolution revealed an irregular β‐helical structure, similar to known homologs. Mutational and molecular docking studies showed that <italic>Col</italic>AFP binds to ice through a compound ice‐binding site (IBS) located at a flat surface of the β‐helix and the adjoining loop region. The IBS of <italic>Col</italic>AFP lacks the repetitive sequences that are characteristic of hyperactive AFPs. These results suggest that <italic>Col</italic>AFP exerts antifreeze activity through a compound IBS that differs from the characteristic IBSs shared by other hyperactive AFPs. This study demonstrates a novel method for protection from freezing by AFPs in psychrophilic microorganisms.</p> </sec> <sec id="febs12878-sec-0002" sec-type="section"> <title>Database</title> <p>Structural data for <italic>Col</italic>AFP have been submitted to the Protein Data Bank (PDB) under accession number <ext-link ext-link-type="uri" xlink:href="http://www.rcsb.org/pdb/search/structidSearch.do?structureId=3WP9" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">3WP9</ext-link>.</p> </sec> </abstract>