PLANT PHYSIOLOGY , Vol 111, Issue 1 293-299, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Purification and Properties of Arabidopsis thaliana COR (Cold-Regulated) Gene Polypeptides COR15am and COR6.6 Expressed in Escherichia coli
S. J. Glimour, C. Lin and M. F. Thomashow
Department of Crop and Soil Sciences (S.J.G, M.F.T), Program in Genetics (C.L, M.F.T), and Department of Microbiology (M.F.T), Michigan State University, East Lansing, Michigan 48824
Arabidopsis thaliana cold-regulated genes COR15a and COR6.6 encode 15- and
6.6-kD polypeptides, respectively. The COR15a polypeptide is known to be
targeted to chloroplasts and, during import, to be processed to a 9.4-kD
polypeptide designated COR15am. The COR6.6 polypeptide is thought to be
located in the cytosol. The coding sequences for COR15am and COR6.6 were
fused to the bacteriophage T7 promoter and expressed in Escherichia coli.
The recombinant polypeptides COR15amr and COR6.6r were purified to near
homogeneity using a combination of ammonium sulfate fractionation,
ion-exchange chromatography, and adsorption chromatography on
hydroxyapatite. COR15amr and the major species of COR15am in chloroplasts
co-migrated on both two-dimensional O'Farrell gels and nondenaturing
polyacrylamide gels. These data corroborate the site of COR15a processing
and indicate no difference in charge or quaternary structure between
COR15amr and the major species of COR15am in plants. In contrast, the
migration patterns of COR6.6r and COR6.6 on two-dimensional gels suggest
that a considerable portion of the COR6.6 population in plants is modified.
In the accompanying papers (M.S. Webb, S.J. Gilmour, M.F. Thomashow, P.L.
Steponkus [1996] Plant Physiology 111: 301-312; M. Uemura, S.J. Gilmour,
M.F. Thomashow, P.L. Steponkus [1996] Plant Physiology 111:313-327), the
effects of COR15amr and COR6.6r on the cryostability and lyotropic phase
behavior of liposomes are examined.