Two non-proline cis peptide bonds may be important for factor XIII function.

The structure of recombinant human cellular factor XIII zymogen was solved in its monoclinic crystal form and refined to an R-factor of 18.3% (Rfree = 23.6%) for all data between 40.0 and 2.1 A resolution. Two non-proline cis peptide bonds were detected. One is between Arg310 and Tyr311 close to the active site cysteine residue (Cys314) and the other is between Gln425 and Phe426 at the dimerization interface. The structure and the role of these cis peptides are discussed in the light of their possible importance for factor XIII function.