Functions as a holding molecular chaperone (holdase) which stabilizes unfolding protein intermediates and rapidly releases them in an active form once stress has abated. Functions as a folding molecular chaperone (foldase) that assists the non-covalent folding of proteins in an ATP-dependent manner (PubMed:23827697). Regulates RPP4-mediated temperature-dependent cell death and defense responses (PubMed:24611624). May assist SGT1B in the formation of SCF E3 ubiquitin ligase complexes that target the immune receptors SNC1, RPS2 and RPS4 for degradation, to regulate receptor levels and avoid autoimmunity (PubMed:24889324). Homodimer. Interacts with OEP61, OEP64 and OM64 (PubMed:24036116). Interacts with SNC1 (PubMed:24889324). Present in all tissues. Most abundantly expressed in roots and floral bud clusters followed by flowers, young fruits and rosette leaves. Expressed in pollen during pollen development, germination and tube growth. Expressed during embryo development and young seedling growth. In contrast to other major heat shock proteins, this one is also expressed at normal growth temperatures. Levels increase only slightly after heat shock and also increase after salt treatment. The TPR repeat-binding motif mediates interaction with TPR repeat-containing proteins. Belongs to the heat shock protein 90 family. Sequencing errors.