Characterization of a Plant Homolog of Hop, a Cochaperone of Hsp90

• Published in: Plant physiology (Bethesda) 2003-02, Vol.131 (2), p.525-535
• Main Authors: Zhang, Zhongming, Michelle K. Quick, Kimon C. Kanelakis, Gijzen, Mark, Krishna, Priti
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Amino acids; Animals; Antibodies; Biological and medical sciences; Carrier Proteins - genetics; Cell biochemistry; Cell physiology; Chitin; Classical and quantitative genetics. Population genetics. Molecular genetics; Cloning, Molecular; Complementary DNA; DNA, Complementary - chemistry; DNA, Complementary - genetics; Environmental Stress and Adaptation; Fundamental and applied biological sciences. Psychology; Gels; Gene Expression Regulation, Plant; Generalities. Genetics. Plant material; Genes. Genome; Genetics and breeding of economic plants; Glycine max - genetics; Glycine max - metabolism; Growth conditions; Heat-Shock Proteins - genetics; Heat-Shock Proteins - metabolism; HSP70 Heat-Shock Proteins - genetics; HSP70 Heat-Shock Proteins - metabolism; HSP90 Heat-Shock Proteins - genetics; HSP90 Heat-Shock Proteins - metabolism; Intermolecular phenomena; Leaves; Mammals; Miscellaneous; Molecular and cellular biology; Molecular biophysics; Molecular Chaperones - genetics; Molecular Chaperones - metabolism; Molecular genetics; Molecular Sequence Data; Multigene Family; Mutation; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Proteins; Rats; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Sequence Homology, Amino Acid; Soybeans; Yeasts
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.011940

The 90-kD molecular chaperone hsp90 is the key component of a multiprotein chaperone complex that facilitates folding, stabilization, and functional modulation of a number of signaling proteins. The components of the animal chaperone complex include hsp90, hsp70, hsp40, Hop, and p23. The animal Hop functions to link hsp90 and hsp70, and it can also inhibit the ATPase activity of hsp90. We have demonstrated the presence of an hsp90 chaperone complex in plant cells, but not all components of the complex have been identified. Here, we report the isolation and characterization of soybean (Glycine max) GmHop-1, a soybean homolog of mammalian Hop. An analysis of soybean expressed sequence tags, combined with preexisting data in literature, suggested the presence of at least three related genes encoding Hop-like proteins in soybean. Transcripts corresponding to Hop-like proteins in soybean were detected under normal growth conditions, and their levels increased further in response to stress. A recombinant GmHop-1 bound hsp90 and its binding to hsp90 could be blocked by the tetratricopeptide repeat (TPR) domain of rat (Rattus norvegicus) protein phosphatase 5. Deletion of amino acids 325 to 395, adjacent to the TPR2A domain in GmHop-1, resulted in loss of hsp90 binding. In a minimal assembly system, GmHop-1 was able to stimulate mammalian steroid receptor folding. These data show that plant and animal Hop homologs are conserved in their general characteristics, and suggest that a Hop-like protein in plants is an important cochaperone of plant hsp90.