Structural and functional analysis of SGT1 reveals that its interaction with HSP90 is required for the accumulation of Rx, an R protein involved in plant immunity.
SGT1 (for suppressor of G2 allele of skp1) and RAR1 (for required for Mla12 resistance) are highly conserved eukaryotic proteins that interact with the molecular chaperone HSP90 (for heat shock protein90). In plants, SGT1, RAR1, and HSP90 are essential for disease resistance triggered by a number of resistance (R) proteins. Here, we present structural and functional characterization of plant SGT1 proteins. Random mutagenesis of Arabidopsis thaliana SGT1b revealed that its CS (for CHORD-SGT1) and SGS (for SGT1 specific) domains are essential for disease resistance. NMR-based interaction surface mapping and mutational analyses of the CS domain showed that the CHORD II domain of RAR1 and the N-terminal domain of HSP90 interact with opposite sides of the CS domain. Functional analysis of the CS mutations indicated that the interaction between SGT1 and HSP90 is required for the accumulation of Rx, a potato (Solanum tuberosum) R protein. Biochemical reconstitution experiments suggest that RAR1 may function to enhance the SGT1-HSP90 interaction by promoting ternary complex formation.
Botër
Marta
M
Sainsbury Laboratory, John Ines Centre, Norwich NR4 7UH, United Kingdom.
Amigues
Béatrice
B
Peart
Jack
J
Breuer
Christian
C
Kadota
Yasuhiro
Y
Casais
Catarina
C
Moore
Geoffrey
G
Kleanthous
Colin
C
Ochsenbein
Francoise
F
Shirasu
Ken
K
Guerois
Raphaël
R
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000276:immunology; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism*; D017124:Conserved Sequence; D005799:Genes, Dominant; D005964:Glucosyltransferases / Q000737:chemistry* / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D007109:Immunity; D007113:Immunity, Innate; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010935:Plant Diseases / Q000276:immunology / Q000821:virology; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D017863:Potexvirus / Q000502:physiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D011198:Solanum tuberosum / Q000201:enzymology* / Q000276:immunology; D012996:Solutions; D014026:Nicotiana / Q000821:virology
D029681:Arabidopsis Proteins; D018841:HSP90 Heat-Shock Proteins; D010940:Plant Proteins; D012996:Solutions; D005964:Glucosyltransferases; C515668:SGT1 protein, Arabidopsis