Format

Send to

Choose Destination
Mol Microbiol. 2015 Oct;98(1):111-29. doi: 10.1111/mmi.13106. Epub 2015 Jul 22.

The TatC component of the twin-arginine protein translocase functions as an obligate oligomer.

Author information

1
Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
2
Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.
3
Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK.

Abstract

The Tat protein export system translocates folded proteins across the bacterial cytoplasmic membrane and the plant thylakoid membrane. The Tat system in Escherichia coli is composed of TatA, TatB and TatC proteins. TatB and TatC form an oligomeric, multivalent receptor complex that binds Tat substrates, while multiple protomers of TatA assemble at substrate-bound TatBC receptors to facilitate substrate transport. We have addressed whether oligomerisation of TatC is an absolute requirement for operation of the Tat pathway by screening for dominant negative alleles of tatC that inactivate Tat function in the presence of wild-type tatC. Single substitutions that confer dominant negative TatC activity were localised to the periplasmic cap region. The variant TatC proteins retained the ability to interact with TatB and with a Tat substrate but were unable to support the in vivo assembly of TatA complexes. Blue-native PAGE analysis showed that the variant TatC proteins produced smaller TatBC complexes than the wild-type TatC protein. The substitutions did not alter disulphide crosslinking to neighbouring TatC molecules from positions in the periplasmic cap but abolished a substrate-induced disulphide crosslink in transmembrane helix 5 of TatC. Our findings show that TatC functions as an obligate oligomer.

PMID:
26112072
PMCID:
PMC5102672
DOI:
10.1111/mmi.13106
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Wiley Icon for PubMed Central
Loading ...
Support Center