It takes two to tango: two TatA paralogues and two redox enzyme-specific chaperones are involved in the localization of twin-arginine translocase substrates in Campylobacter jejuni

Abstract

The food-borne zoonotic pathogen Campylobacter jejuni has complex electron transport chains required for growth in the host, many of which contain cofactored periplasmic enzymes localized by the twin-arginine translocase (TAT). We report here the identification of two paralogues of the TatA translocase component in C. jejuni strain NCTC 11168, encoded by cj1176c (tatA1) and cj0786 (tatA2). Deletion mutants constructed in either or both of the tatA1 and tatA2 genes displayed distinct growth and enzyme activity phenotypes. For sulphite oxidase (SorAB), the multi-copper oxidase (CueO) and alkaline phosphatase (PhoX), complete dependency on TatA1 for correct periplasmic activity was observed. However, the activities of nitrate reductase (NapA), formate dehydrogenase (FdhA) and trimethylamine N-oxide reductase (TorA) were significantly reduced in the tatA2 mutant. In contrast, the specific rate of fumarate reduction catalysed by the flavoprotein subunit of the methyl menaquinone fumarate reductase (MfrA) was similar in periplasmic fractions of both the tatA1 and the tatA2 mutants and only the deletion of both genes abolished activity. Nevertheless, unprocessed MfrA accumulated in the periplasm of the tatA1 (but not tatA2) mutant, indicating aberrant signal peptide cleavage. Surprisingly, TatA2 lacks two conserved residues (Gln8 and Phe39) known to be essential in Escherichia coli TatA and we suggest it is unable to function correctly in the absence of TatA1. Finally, only two TAT chaperones (FdhM and NapD) are encoded in strain NCTC 11168, which mutant studies confirmed are highly specific for formate dehydrogenase and nitrate reductase assembly, respectively. Thus, other TAT substrates must use general chaperones in their biogenesis.

Campylobacter jejuni CsrA Regulates Metabolic and Virulence Associated Proteins and Is Necessary for Mouse Colonization

“…Abundance of a number of proteins that are involved in providing electrons for respiration is also altered in the csrA mutant, some with greater and some with lesser expression. NuoI [ 28 ] and PFOR [ 29 ] are more highly expressed during stationary phase, while the respiratory proteins MfrA [ 30 – 32 ], TorA [ 32 , 33 ], and Cj0414 [ 16 ] are less abundant. The altered expression of these proteins suggests that CsrA controls aspects of cellular respiration, especially at stationary phase.…”

A Tat ménage à trois — The role of Bacillus subtilis TatAc in twin-arginine protein translocation

“…Recent studies in Helicobacter pylori and Campylobacter jejuni have highlighted that of the two TatA-like proteins present only one is essential for functional translocation [72,73]. In contrast, E. coli has two essential TatA-like proteins (TatA and TatB), but both of these proteins can be functionally replaced by a single B. subtilis TatA protein [30,44].…”

Bacterial molybdoenzymes: old enzymes for new purposes

“…The nap locus encodes also an additional cytoplasmic protein of around 9 kDa, named NapD, which contains a ferredoxin-like fold (Dow et al 2013). The absence of NapD leads to a loss of NapA activity in E. coli and Campylobacter jejuni and to the absence of the NapA protein in Wolinella succinogenes (Potter et al 2001;Kern, Mager and Simon 2007;Liu et al 2014). Therefore, NapD might influence NapA stability.…”