The expression, processing and localization of polymorphic membrane proteins in Chlamydia pneumoniae strain CWL029

Ten Pmps were identified in elementary bodies (EBs). Eight of these were investigated with respect to time dependent expression and all were found to be up-regulated between 36 and 48 hours post infection. Antibodies against Pmp6, 8, 10, 11 and 21 reacted with chlamydiae when infected cells were formalin fixed. Pmp6, Pmp20 and Pmp21 were found in cleaved forms, and the cleavage sites of Pmp6 and Pmp21 were identified.The Pmps are heavily up-regulated at the time of conversion of RB to EB, and at least ten Pmps are present in EBs. Due to their reaction in formalin fixation it is likely that Pmp6, 8, 10, 11 and 21 are surface exposed. The identified cleavage sites of Pmp6 and Pmp21 are in agreement with the theory that the Pmps are autotransporters.Chlamydiae are pathogenic gram-negative bacteria of which C. pneumoniae causes upper and lower respiratory tract infections in humans [1]. Going through a developmental cycle the chlamydiae alternate between infective elementary bodies (EBs) and replicative reticulate bodies (RBs) [2]. The bacteria are obligate and intracellular, residing inside a specialized phagosome, named the chlamydial inclusion. The duration of the developmental cycle for C. pneumoniae cultivated in cell culture is about 72 hours [3].The C. pneumoniae CWL029 genome sequence revealed the presence of a gene family, the pmp family, consisting of 21 members [4] that were paralogous to the pmps found in C. trachomatis [5] and C. psittaci [6-9]. The C. psittaci Pmps have been analysed by two-dimensional electrophoresis in an earlier study [37]. The Pmps are two-domain proteins with similarity to autotransporter proteins [4,10,11]. They are characterized by a high frequency of the two sequences FxxN and GGAI in the N-terminal part (twelve and seven repeats on average, respectively) [4], and their C-terminal part shows the characteristics of a β-barrel [10]. The GGAI motif and the prediction of a C-terminal β-barrel suggest that the Pmps are autotransporters,