STRUCTURE OF THE TWO-PARTNER SECRETION PROTEIN SHLB FROM SERRATIA MARCESCENS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Many large virulence proteins of pathogenic gram-negative bacteria are secreted by the Two-partner secretion (TPS) pathway. As the name implies, only two proteins are required for this process: the secreted exoprotein (TpsA) and the ¿}¿¿-barrel transport channel in the OM (TpsB). After crossing the inner membrane via the SecY complex, TpsA is likely translocated across the OM in an unfolded state. Many aspects of the transport process are unclear: how is periplasmic TpsA kept soluble, how does targeting to the OM channel occur, and how is TpsA transported through the TpsB channel, given that no external energy is required? To begin answer these questions we plan to crystallize a TpsB channel. The TpsB proteins are distantly related to the Omp85 family, which are involved in the biogenesis of OM proteins. Members of this family are also present in eukaryotes (mitochondria). Both for TPS and Omp85 family members no structural information is known at present.