Cystatin SN, or, CST1, is a human gene. Other names include: Cystatin-SN; Cystain-SA-I; Cystatin-1; Salivary cystatin-SA-1. The encoded protein has an amino acid length of 141 and a mass of 16.4 kDa. Cystatin SN is a member of the Cystatin family. This gene shares homology with other species, including: Nematode.