Component of the FACT complex, a general chromatin factor that acts to reorganize nucleosomes. The FACT complex is involved in multiple processes that require DNA as a template such as mRNA elongation, DNA replication and DNA repair. During transcription elongation the FACT complex acts as a histone chaperone that both destabilizes and restores nucleosomal structure. It facilitates the passage of RNA polymerase II and transcription by promoting the dissociation of one histone H2A-H2B dimer from the nucleosome, then subsequently promotes the reestablishment of the nucleosome following the passage of RNA polymerase II (By similarity). Forms a stable heterodimer with pob3 (By similarity). The spt16-pob3 dimer weakly associates with multiple molecules of nhp6 to form the FACT complex (By similarity). Interacts with abo1 (PubMed:26582768). Belongs to the peptidase M24 family. SPT16 subfamily. Although related to the peptidase M24 family, this protein lacks conserved active site residues suggesting that it may lack peptidase activity.