Anti-15.5K antibodies are protein reagents that detect specific antigens. The 15.5K antigen is another term for the human protein small nuclear ribonucleoprotein 13, encoded by the SNU13 gene. The protein is known to be a part of the small subunit (SSU) processome, first precursor of the small eukaryotic ribosomal subunit. Canonically, it has an amino acid length of 128 residues and a mass of 14.2 kilodaltons. Its subcellular localization is in the nucleus and it is ubiquitously expressed across many tissue types. The 15.5K protein is a member of the Eukaryotic ribosomal protein eL8 protein family. Other alias names for 15.5K include FA-1 and FA1.