Interconvertibility of lipid- and translocon-bound forms of the bacterial Tat precursor pre-SufI.
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Signal peptides target protein cargos for secretion from the bacterial cytoplasm. These signal peptides contain a tri-partite structure consisting of a central hydrophobic domain (h-domain), and two flanking polar domains. Using a recently developed in vitro transport assay, we report here that a central h-domain position (C17) of the twin arginine translocation (Tat) substrate pre-SufI is especially sensitive to amino acid hydrophobicity. The C17I mutant is transported more efficiently than wild type, whereas charged substitutions completely block transport. Transport efficiency is well-correlated with Tat translocon binding efficiency. The precursor protein also binds to non-Tat components of the membrane, presumably to the lipids. This lipid-bound precursor can be chased through the Tat translocons under conditions of high proton motive force. Thus, the non-Tat bound form of the precursor is a functional intermediate in the transport cycle. This intermediate appears to directly equilibrate with the translocon-bound form of the precursor.
author list (cited authors)
Bageshwar, U. K., Whitaker, N., Liang, F., & Musser, S. M.
complete list of authors
Bageshwar, Umesh K||Whitaker, Neal||Liang, Fu-Cheng||Musser, Siegfried M