Characterization of plant p23-like proteins for their co-chaperone activities.
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.
Zhang
Zhongming
Z
Department of Biology, The University of Western Ontario, 1151 Richmond St. N., London, ON N6A 5B7, Canada.
Sullivan
William
W
Felts
Sara J
SJ
Prasad
Bishun D
BD
Toft
David O
DO
Krishna
Priti
P
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
D029681:Arabidopsis Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D010940:Plant Proteins; D000255:Adenosine Triphosphate