title: Characterization of plant p23-like proteins for their co-chaperone activities.
abstract: The small acidic protein p23 is best described as a co-chaperone of Hsp90, an essential molecular chaperone in eukaryotes. p23 binds to the ATP-bound form of Hsp90 and stabilizes the Hsp90-client protein complex by slowing down ATP turnover. The stabilizing activity of p23 was first characterized in studies of steroid receptor-Hsp90 complexes. Earlier studies of the Hsp90 chaperone complex in plants suggested that a p23-like stabilizing activity was absent in plant cell lysates. Here, we show that p23-like proteins are present in plants and are capable of binding Hsp90, but unlike human p23 and yeast ortholog Sba1, the plant p23-like proteins do not stabilize the steroid receptor-Hsp90 complexes formed in wheat germ lysate. Furthermore, these proteins do not inhibit the ATPase activity of plant Hsp90. While transcripts of Arabidopsis thaliana p23-1 and Atp23-2 were detected under normal growing conditions, those of the closely related Brassica napus p23-1 were present only after moderate heat stress. These observations suggest that p23-like proteins in plants are conserved in their binding to Hsp90 but have evolved mechanisms of action different from their yeast and animal counterparts.
authors.affiliation: Department of Biology, The University of Western Ontario, 1151 Richmond St. N., London, ON N6A 5B7, Canada.
authors.forename: Zhongming
authors.initials: Z
authors.lastname: Zhang
authors.forename: William
authors.initials: W
authors.lastname: Sullivan
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Felts
authors.forename: Bishun D
authors.initials: BD
authors.lastname: Prasad
authors.forename: David O
authors.initials: DO
authors.lastname: Toft
authors.forename: Priti
authors.initials: P
authors.lastname: Krishna
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001937:Brassica / Q000235:genetics / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D029681:Arabidopsis Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D010940:Plant Proteins; D000255:Adenosine Triphosphate