Molecular cloning of the major outer membrane protein of Chlamydia trachomatis

A gene library of Chlamydia trachomatis (serovar L1) DNA has been prepared in the phage vector lambda 1059. From this bank, 20 recombinant phage-expressing components which reacted with serum from a patient with a C. trachomatis (L1) infection were chosen. Selective expression and radiolabeling of phage polypeptides in irradiated Escherichia coli demonstrated that one of these clones encoded a polypeptide doublet with an apparent molecular weight similar to that of the C. trachomatis (L1) major outer membrane protein. Both species of this cloned doublet (40 and 41 kilodaltons) could be immunoprecipitated by serum from a patient with a C. trachomatis (L1) infection but not by normal human serum. Components of this apparent molecular weight were not precipitated from irradiated E. coli infected with vector phage lambda 1059 by either of these sera. Comparison of the Staphylococcus aureus-V8 protease peptide maps of these two cloned polypeptides and chlamydial major outer membrane protein extracted from elementary bodies showed all three polypeptides to produce peptide fragments of 15.5, 13.8, and 11.5 kilodaltons. Due to the identical apparent molecular weights of the fragments produced from the 40- and 41-kilodalton cloned polypeptides, these were concluded to be different conformational forms of the same molecular species. These cloned components were indistinguishable from C. trachomatis (L1) major outer membrane protein.