Identification of T. pallidum polypeptides: a comparative study between the protein profiles of in vitro cultivated and in vivo propagated Treponema pallidum subsp. pallidum by two-dimensional polyacrylamide gel electrophoresis.

Protein profiles of in vivo propagated and in vitro cultivated Treponema pallidum subsp. pallidum (Nichols strain) were analyzed using two-dimensional gel electrophoresis (2D-PAGE). A comparative study between the two protein profiles (as detected by silver stain, Western blotting, and autoradiography) demonstrated two in vitro synthesized polypeptides with approximate molecular masses of 29- and 35 kDa (both with pI 5.62) which were absent in the protein profile of the in vivo propagated T. pallidum. It also was demonstrated that the in vitro cultivated organisms lacked an antigenic polypeptide (as judged by Western blots) of approximate molecular weight 35 kDa (pI 5.34) which was present in the in vivo propagated organisms. To determine the cellular location of these polypeptides, the outer membrane proteins of T. pallidum was extracted with Triton X-114. The extracted proteins were subjected to phase partitioning and the 2D-PAGE protein profiles of the detergent and aqueous phases were compared. The results indicated that in vitro cultivation caused some changes in the cytoplasmic protein profiles of T. pallidum, but no changes were detected in the profiles of the membrane proteins.