Production and crystallization of the C-propeptide trimer from human procollagen III

The C‐propeptide domains of the fibrillar procollagens, which are present throughout the Metazoa in the form of ∼90 kDa trimers, play crucial roles in both intracellular molecular assembly and extracellular formation of collagen fibrils. The first crystallization of a C‐propeptide domain, that from human procollagen III, is described. Following transient expression in mammalian 293T cells of both the native protein and a selenomethionine derivative, two crystal forms of the homotrimer were obtained: an orthorhombic form (P212121) that diffracted to 1.7 Å resolution and a trigonal form (P321) that diffracted to 3.5 Å resolution. Characterization by MALDI‐TOF mass spectrometry allowed the efficiency of selenomethionine incorporation to be determined.