A heterotetrameric protein complex involved in the sulfur-relay system required for 2-thiolation of 5-methylaminomethyl-2-thiouridine (mnm5s2U) at tRNA wobble positions. In E. coli it consists of a central IscS dimer with the two TusA protomers bound to one of the IscS units each via persulfide (-SSH) groups.
IscS-TusA complex