| The Escherichia coli Tat system transports fully folded proteins across the cytoplasmic membrane. Substrates for the Tat system include redox proteins, necessary for anaerobic respiration. The transport of substrates, which are responsible for N- and S-oxide respiration, DmsAB and TorA, are dependent on system specific chaperones, DmsD and TorD respectively. Both belong to the redox enzyme maturation proteins (REMP) family and play multiple roles in the maturation and export of specific redox enzymes. We propose that REMPs may exhibit nucleotide binding and hydrolysis like other general chaperones. This work shows that both DmsD and TorD are capable of binding and hydrolyzing GTP, confirming previous findings for TorD. Additionally, a unique folding form of TorD was identified to have increased GTPase activity. Finally, bioinformatically derived putative binding sites were experimentally explored, resulting in the implication of residues from predictions to be involved in GTP binding. |
