Component of the ribosome-associated complex (RAC), a heterodimeric chaperone complex involved in regulation of accurate translation termination and in folding or maintaining nascent polypeptides in a folding-competent state. RAC stimulates the ATPase activity of the ribosome-associated pool of Hsp70-type chaperones SSB1/SSB2 that bind to the nascent polypeptide chain. SSZ1 is required for ZUO1 to function efficiently as a J-protein for SSB1/SSB2. Also involved in pleiotropic drug resistance by post-translational activation of transcription factor PDR1