English: Inactive human blood clotting factor XIII (PDB: 1EVU), a transglutaminase. Homodimer of catalytic A1 peptides (gene F13A1) is shown. XIII in human blood is actually a heterotetramer of 2 A1 peptides and 2 B peptides (gene F13B). B peptides are not shown, but would form a ring-like structure around the A1 dimer.

N- & C-terminals are shown as "N" and "C". Protein on the left is rotated 90° about its y-axis and the result is on the right.

Domains:

• Magenta (N-terminal): activation peptide, which is removed when XIII is activated to XIIIa
• Cyan: β-sandwich
• Green: catalytic core (orange: catalytic amino acid residues C314, H373-D396 and W279 are shown)
• Blue: β-barrel 1
• Red (C-terminal): β-barrel 2

Sructure from www.rcsb.org. Source for info:

• Muszbek L et al (2011). Physiological Reviews. 91 (3): 931–972. Doi:10.1152/physrev.00016.2010