[3P-04] Molecular basis of interaction between the human ceramide transport protein CERT and the Chlamydia trachomatis membrane protein IncD
In mammalian cells, the ceramide transport protein (CERT) transports ceramide from the endoplasmic reticulum (ER) to the Golgi apparatus. Human CERT is essential for the obligate intracellular bacterium Chlamydia trachomatis to proliferate in human cells. C. trachomatis forms a vacuole named "inclusion", in which it replicates. The inclusion-resident membrane protein IncD recruits CERT to the inclusion by binding to the CERT PH domain, thereby redirecting host ceramide from the ER to the inclusion. The PH domain of OSBP, an oxysterol-transfer protein, is not recognized by IncD although its primary sequence is highly similar to that of the CERT PH domain. We here explored how IncD specifically recognizes the CERT PH domain by solution NMR experiments. We first determined the tertiary structure of the OSBP PH domain. Then, to identify amino acid residues of the CERT PH domain that specifically participate in interaction with IncD, we performed a comparative analysis about chemical shift perturbation of the CERT PH and the OSBP PH domains by titrating a recombinant soluble IncD. Its results revealed that IncD captures specific sites of the surface of the CERT PH domain in a tweezer-like manner.