title: Structure and in vitro molecular chaperone activity of cytosolic small heat shock proteins from pea.
abstract: Plants synthesize several classes of small heat shock proteins ranging in size from 15 to 30 kDa. Two conserved classes, designated class I and class II, are localized to the cytosol. Recombinant HSP18.1 and HSP17.7, representing class I and class II proteins from pea, respectively, were expressed in Escherichia coli and purified. Non-denaturing polyacrylamide gel electrophoresis and electron microscopy demonstrated that the purified proteins formed discretely sized, high molecular weight complexes. Sedimentation equilibrium analytical ultracentrifugation revealed that the HSP18.1 and HSP17.7 complexes were composed of approximately 12 subunits. Both proteins were able to enhance the refolding of chemically denatured citrate synthase and lactate dehydrogenase at stoichiometric levels in an ATP-independent manner. Furthermore, HSP18.1 and HSP17.7 prevented aggregation of citrate synthase at 45 degrees C and irreversible inactivation of citrate synthase at 38 degrees C. HSP18.1 also suppressed aggregation of lactate dehydrogenase at 55 degrees C. These findings demonstrate that HSP18.1 and HSP17.7 can function as molecular chaperones in vitro.
authors.affiliation: Department of Biochemistry, University of Arizona, Tucson 85721, USA.
authors.forename: G J
authors.initials: GJ
authors.lastname: Lee
authors.forename: N
authors.initials: N
authors.lastname: Pokala
authors.forename: E
authors.initials: E
authors.lastname: Vierling
mesh_terms: D002950:Citrate (si)-Synthase / Q000737:chemistry; D003600:Cytosol / Q000737:chemistry; D006360:Heat-Shock Proteins / Q000502:physiology*; D006358:Hot Temperature; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000737:chemistry; D008854:Microscopy, Electron; D018832:Molecular Chaperones; D008970:Molecular Weight; D018532:Pisum sativum / Q000502:physiology*; D010940:Plant Proteins / Q000502:physiology; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D011994:Recombinant Proteins
chemical_list: D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D010940:Plant Proteins; D011994:Recombinant Proteins; D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase