Figure 4

The cHtrA but not CT067 is detected in the cytosolic fraction of the chlamydia-infected HeLa cells. HeLa cells infected with C. trachomatis organisms (Ct-HeLa) were fractionated into nuclear (Ct-HeLa pellet, containing chlamydial inclusions, lane 3) and cytosolic (Ct-HeLa S100, containing chlamydia-secreted proteins, lane 4) fractions. The cellular fractions along with total cell lysates (normal HeLa, lane 1 & Ct-HeLa, lane 2) and purified chlamydial RB (lane 5) and EB (lane 6) organisms as listed at the top were resolved in SDS-polyacrylamide gels. The resolved protein bands were blotted onto nitrocellulose membrane for reacting with antibodies (listed on the left) against cHtrA (panel a), CT067 (b, a periplasmic iron binding protein), CPAF (c, a chlamydia-secreted protein), MOMP (d, a chlamydial outer membrane protein) and human HSP70 (e, a host cell cytosolic protein). All antibodies detected their corresponding proteins in the HeLa-L2 whole-cell lysate sample (lane 2) and other corresponding samples (as indicated on the right). Note that both cHtrA and CPAF but not CT067 or MOMP were detected in the cytosolic fraction (lane 4). CPAFc represents the C-terminal fragment of CPAF processed during chlamydial infection. The cHtrA degradation fragments (likely produced during in vitro sample processing) can always be detected with varying levels as HtrA is a powerful serine protease known to cleave itself [61] under certain conditions.