Cytosolic mediator for sorting and targeting of nascent chloroplast outer envelope membrane (OEM) proteins to the chloroplast. Functions as a AKR2A cofactor to facilitates the targeting of OEP7 to chloroplasts. Homodimer under normal physiological conditions. Aggregates in high oligomeric complexes after heat shock. Binds to AKR2A and to chloroplasts. Expressed ubiquitously at low levels under normal physiological conditions. Accumulates after heat shock. Reduction of OEP7 targeting to plastids. Belongs to the small heat shock protein (HSP20) family.