3.1.1.27 ? x * 31000, SDS-PAGE 3.1.1.27 dimer 2 * 28000, SDS-PAGE 3.1.1.27 dimer 2 * 31000, SDS-PAGE, 2 * 29855, calculated 3.1.1.27 homodimer x-ray crystallography 3.1.1.27 additional information N-terminal amino acid sequence