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Translocator Proteins in the Two-partner Secretion Family Have Multiple Domains
Journal article   Open access   Peer reviewed

Translocator Proteins in the Two-partner Secretion Family Have Multiple Domains

Neeraj K. Surana, Amy Z. Buscher, Gail G. Hardy, Susan Grass, Thomas Kehl-Fie and Joseph W. St. Geme
The Journal of biological chemistry, Vol.281(26), pp.18051-18058
06/30/2006
DOI: 10.1074/jbc.M600036200
PMID: 16648638
url
https://doi.org/10.1074/jbc.M600036200View
Published (Version of record) Open Access

Abstract

The two-partner secretion pathway in Gram-negative bacteria consists of a TpsA exoprotein and a cognate TpsB outer membrane translocator protein. Previous work has demonstrated that the TpsB protein forms a β-barrel structure with pore forming activity and facilitates translocation of the TpsA protein across the outer membrane. In this study, we characterized the functional domains of the Haemophilus influenzae HMW1B protein, a TpsB protein that interacts with the H. influenzae HMW1 adhesin. Using c-Myc epitope tag insertions and cysteine substitution mutagenesis, we discovered that HMW1B contains an N-terminal surface-localized domain, an internal periplasmic domain, and a C-terminal membrane anchor. Functional and biochemical analysis of the c-Myc epitope tag insertions and a series of HMW1B deletion constructs demonstrated that the periplasmic domain is required for secretion of HMW1 and that the C-terminal membrane anchor (HMW1B-(234–545)) is capable of oligomerization and pore formation. Similar to our observations with HMW1B, examination of a Bordetella pertussis TpsB protein called FhaC revealed that the C terminus of FhaC (FhaC-(232–585)) is capable of pore formation. We speculate that all TpsB proteins have a modular structure, with a periplasmic domain that interacts with the cognate TpsA protein and with pore forming activity contained within the C terminus.

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