FIG. 1.

NMR structure of protein S and map of the pCold-PST vector. (a) NMR structure of M. xanthus protein S with Ca²⁺ ions bound (3). (b) Structure and schematic map of pCold-PST_TEV or pCold-PST_Xa. (c) Schematic presentation of a PrS₂ fusion protein. Two tandem repeats of the NTD of protein S (amino acids 1 to 92; PrS₂) are fused at the N-terminal end of a protein of interest, and a short linker which contains a protease cleavage site is added between the PrS₂ tag and the target protein. (d) Expression of PrS₂. Aliquots of a culture growing at 15°C were removed at 0, 12, and 24 h after induction with 1 mM IPTG and analyzed by SDS-PAGE. (e) Solubility of PrS₂ as determined using a culture aliquot obtained 24 h after induction. M13 IG, intergenic region of M13 bacteriophage; UTR, untranslated region; W, whole-cell lysate; S, soluble fraction; I, insoluble fraction of PrS₂.