PDBsum entry 1hg7

Antifreeze protein

PDB id: 1hg7

Contents

Protein chain

66 a.a. *

Ligands

SO4

Waters ×154

* Residue conservation analysis

PDB id:

1hg7

Name:

Antifreeze protein

Title:

High resolution structure of hplc-12 type iii antifreeze protein from ocean pout macrozoarces americanus

Structure:

Hplc-12 type iii antifreeze protein. Chain: a. Engineered: yes. Mutation: yes

Source:

Macrozoarces americanus. Ocean pout. Organism_taxid: 8199. Variant: hplc-12 component. Tissue: blood serum. Gene: recombinant type iii afp hpurce 10 fraction 12. Expressed in: escherichia coli. Expression_system_taxid: 469008. 12

Resolution:

1.15Å R-factor: 0.120 R-free: 0.169

Authors:

A.A.Antson,D.J.Smith,D.I.Roper,S.Lewis,L.S.D.Caves,C.S.Verma, S.L.Buckley,P.J.Lillford,R.E.Hubbard

Key ref:

A.A.Antson et al. (2001). Understanding the mechanism of ice binding by type III antifreeze proteins. J Mol Biol, 305, 875-889. PubMed id: 11162099 DOI: 10.1006/jmbi.2000.4336

Date:

13-Dec-00 Release date: 31-Jan-01

Protein chain

P19614  (ANP12_ZOAAM) -  Type-3 ice-structuring protein HPLC 12 from Zoarces americanus

Seq: 66 a.a.

Struc: 66 a.a.*

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

DOI no: 10.1006/jmbi.2000.4336

J Mol Biol 305:875-889 (2001)

PubMed id: 11162099

Understanding the mechanism of ice binding by type III antifreeze proteins.

A.A.Antson, D.J.Smith, D.I.Roper, S.Lewis, L.S.Caves, C.S.Verma, S.L.Buckley, P.J.Lillford, R.E.Hubbard.

ABSTRACT

Type III antifreeze proteins (AFPs) are present in the body fluids of some polar fishes where they inhibit ice growth at subzero temperatures. Previous studies of the structure of type III AFP by NMR and X-ray identified a remarkably flat surface on the protein containing amino acids that were demonstrated to be important for interaction with ice by mutational studies. It was proposed that 0) plane of ice with the key amino acids interacting directly with the water molecules in the ice crystal. Here, we show that the mechanism of type III AFP interaction with ice crystals is more complex than that proposed previously. We report a high-resolution X-ray structure of type III AFP refined at 1.15 A resolution with individual anisotropic temperature factors. We report the results of ice-etching experiments that show a broad surface coverage, suggesting that type III AFP binds to a set of planes that are parallel with or inclined at a small angle to the crystallographic c-axis of the ice crystal. Our modelling studies, performed with the refined structure, confirm that type III AFP can make energetically favourable interactions with several ice surfaces.

Selected figure(s)

Figure 3.
Figure 3. Stereo figures of two regions of the ice-binding surface showing known X-ray structures of type III AFP. (a) The region around Gln9 and Thr18. (b) The region around Asn14 and Gln44. The X-ray structure of the HPLC12 type III ocean pout AFP, determined in the present study (shown in blue), is overlapped with the previously determined structure (shown in red; [Jia et al 1996]) and with the structure of the HPLC3 isoform [Yang et al 1998].

Figure 4.
Figure 4. Results of the ice-etching experiment. Left, Photograph of etched ice hemisphere grown in the presence of HPLC-12 type III AFP from ocean pout. Right, A representation of the etched pattern. The etched surfaces, where the antifreeze protein bound to the ice crystal, are shaded. The unshaded regions represent ice surfaces that have remained mirror-like and do not have bound protein molecules. The positions of the crystallographic a-axis and c-axis are shown in the centre of the Figure.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2001, 305, 875-889) copyright 2001.

Figures were selected by an automated process.