Catalyzes the removal of elemental sulfur from cysteine to produce alanine. It supplies the inorganic sulfur for iron-sulfur (Fe-S) clusters. [sulfur carrier]-H + L-cysteine = [sulfur carrier]-SH + L-alanine L-cysteine binding is slower in the presence of bcn92 and IscU (PubMed:29491838). Activation requires bcn92, IscU and fh (PubMed:29491838). Interacts with bcn92 and IscU (PubMed:29491838). Might form a complex with bcn92, IscU and fh (Probable). Ubiquitous expression at high levels in any life stage. Belongs to the class-V pyridoxal-phosphate-dependent aminotransferase family. NifS/IscS subfamily.