X-Message-Number: 11548
Date: Tue, 13 Apr 1999 06:55:50 -0700 (PDT)
From: Doug Skrecky <>
Subject: insect antifreeze

Authors
  Li N.  Andorfer CA.  Duman JG.
Institution
  Department of Biological Sciences, University of Notre Dame, Notre Dame, IN
  46556, USA.
Title
  Enhancement of insect antifreeze protein
  activity by solutes of low molecular mass.
Source
  Journal of Experimental Biology.  201 ( Pt 15):2243-51, 1998 Aug.
Abstract
  Antifreeze proteins (AFPs) lower the non-equilibrium freezing point of water
  (in the presence of ice) below the melting point, thereby producing a
  difference between the freezing and melting points that has been termed
  thermal hysteresis. In general, the magnitude of the thermal hysteresis
  depends upon the specific activity and concentration of the AFP. This study
  describes several low-molecular-mass solutes that enhance the thermal
  hysteresis activity of an AFP from overwintering larvae of the beetle
  Dendroides canadensis. The most active of these is citrate, which increases
  the thermal hysteresis nearly sixfold from 1.2 degrees C in its absence to
  6.8 degrees C. Solutes which increase activity approximately fourfold are
  succinate, malate, aspartate, glutamate and ammonium sulfate. Glycerol,
  sorbitol, alanine and ammonium bicarbonate increased thermal hysteresis
  approximately threefold. Interestingly, 0.5 mol l-1 sodium sulfate eliminated
  activity. Solute concentrations between 0.25 and 1 mol l-1 were generally
  required to elicit optimal thermal hysteresis activity. Glycerol is the only
  one of these enhancing solutes that is known to be present at these
  concentrations in overwintering D. canadensis, and therefore the
  physiological significance of most of these enhancers is unknown. The
  mechanism(s) of this enhancement is also unknown. The AFP
  used in this study (DAFP-4) is nearly identical to previously described D.
  canadensis AFPs. The mature protein consists of 71 amino acid residues
  arranged in six 12- or 13-mer repeats with a consensus sequence consisting of
  Cys-Thr-X3-Ser-X5-X6-Cys-X8-X9-Ala-X11-Thr-X1 3, where X3 and X11 tend to be
  charged residues, X5 tends to be Thr or Ser, X6 to be Asn or Asp, X9 to be
  Asn or Lys and X13 to be Ala in the 13-mers. DAFP-4 is shorter by one repeat
  than previously described D. canadensis AFPs.

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