Cargo protein of a type 2A encapsulin nanocompartment involved in sulfur metabolism. Cysteine desulfurases mobilize the sulfur from L-cysteine to yield L-alanine, an essential step in sulfur metabolism for biosynthesis of a variety of sulfur-containing biomolecules. [sulfur carrier]-H + L-cysteine = [sulfur carrier]-SH + L-alanine Isolated from bacteria in a complex with encapsulin 2A (AC I3NID5), strongly suggesting it is found in a type 2A encapsulin nanocompartment (PubMed:25500374). There are 1-2 copies of this protein in each encapsulin shell (By similarity). Cattle naturally infected with M.paratuberculosis have antisera that recognize this protein. Belongs to the class-V pyridoxal-phosphate-dependent aminotransferase family. Csd subfamily. Truncated N-terminus.