Two-dimensional electrophoretic analysis of the protein family at 90 kDa of abortifacient Chlamydia psittaci

Four major clusters, designated A, B, C and D, were distinguished in Western Blots by a monoclonal antibody specific for the ''antigen family at 90 kDa'' after two-dimensional electrophoretic analysis on immobilized pH gradient of chlamydial elementary bodies of abortifacient C. psittaci. Clusters B, C, and D were closely related with molecular mass (kDa) pI values of 91.5/5.2-5.4, 90/5.0-5.2 and 90.5/5.6-5.8, respectively. Cluster A was larger, with molecular mass/pI of 104.7/5.1-5.3. Evidence for the antigenic relationship between cluster A and clusters B, C and D was further supported by immunological cross-reaction with affinity-purified antibodies from serum of ewes with chlamydial-induced abortion. The experimental values obtained for size and pI of the four clusters correlated well with the calculated values from known sequences coded by multiple chlamydial genes. Direct evidence for the correspondence between the immunoreactive clusters B, C and D and the retrieved genes was provided by antibody binding experiments to recombinant polypeptides representing fragments of the deduced proteins. The 4-member antigen family at 90/104 kDa is the first example of proteins coded by multiple genes within the genus Chlamydia.