Overlapping functions of components of a bacterial Sec-independent protein export pathway.
We describe the identification of two Escherichia coli genes required for the export of cofactor-containing periplasmic proteins, synthesized with signal peptides containing a twin arginine motif. Both gene products are homologous to the maize HCF106 protein required for the translocation of a subset of lumenal proteins across the thylakoid membrane. Disruption of either gene affects the export of a range of such proteins, and a complete block is observed when both genes are inactivated. The Sec protein export pathway was unaffected, indicating the involvement of the gene products in a novel export system. The accumulation of active cofactor-containing proteins in the cytoplasm of the mutant strains suggests a role for the gene products in the translocation of folded proteins. One of the two HCF106 homologues is encoded by the first gene of a four cistron operon, tatABCD, and the second by an unlinked gene, tatE. A mutation previously assigned to the hcf106 homologue encoded at the tatABCD locus, mttA, lies instead in the tatB gene.
Sargent
F
F
Nitrogen Fixation Laboratory, John Innes Centre, Colney, Norwich NR4 7UH.
Bogsch
E G
EG
Stanley
N R
NR
Wexler
M
M
Robinson
C
C
Berks
B C
BC
Palmer
T
T
D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D001692:Biological Transport; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004269:DNA, Bacterial; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D005560:Formate Dehydrogenases / Q000378:metabolism; D005798:Genes, Bacterial; D006864:Hydrogenase / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D010940:Plant Proteins; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C109236:Hcf106 protein, plant; D008565:Membrane Proteins; D010940:Plant Proteins; D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; D006864:Hydrogenase; D005560:Formate Dehydrogenases; D010089:Oxidoreductases, N-Demethylating; C023186:trimethylamine dehydrogenase