TY - JOUR
T1 - Remnant signal peptides on non-exported enzymes
T2 - implications for the evolution of prokaryotic respiratory chains
AU - Ize, Berengere
AU - Coulthurst, Sarah J.
AU - Hatzixanthis, Kostas
AU - Caldelari, Isabelle
AU - Buchanan, Grant
AU - Barclay, Elaine C.
AU - Richardson, David J.
AU - Palmer, Tracy
AU - Sargent, Frank
PY - 2009/12
Y1 - 2009/12
N2 - The twin-arginine translocation (Tat) pathway is a prokaryotic protein targeting system dedicated to the transmembrane translocation of folded proteins. Substrate proteins are directed to the Tat translocase by signal peptides bearing a conserved SRRxFLK 'twin-arginine' motif. In Escherichia coli, most of the 27 periplasmically located Tat substrates are cofactor-containing respiratory enzymes, and many of these harbour a molybdenum cofactor at their active site. Molybdenum cofactor-containing proteins are not exclusively located in the periplasm, however, with the major respiratory nitrate reductase (NarG) and the biotin sulfoxide reductase (BisC), for example, being located at the cytoplasmic side of the membrane. Interestingly, both NarG and Bisc contain 'N-tail' regions that bear some sequence similarity to twin-arginine signal peptides. In this work, we have examined the relationship between the non-exported N-tails and the Tat system. Using a sensitive genetic screen for Tat transport, variant N-tails were identified that displayed Tat transport activity. For the NarG 36-residue N-tail, six amino acid changes were needed to induce transport activity. However, these changes interfered with binding by the NarJ biosynthetic chaperone and impaired biosynthesis of the native enzyme. For the BisC 36-residue N-tail, only five amino acid substitutions were needed to restore Tat transport activity. These modifications also impaired in vivo BisC activity, but it was not possible to identify a biosynthetic chaperone for this enzyme. These data highlight an intimate genetic and evolutionary link between some non-exported redox enzymes and those transported across membranes by the Tat translocation system.
AB - The twin-arginine translocation (Tat) pathway is a prokaryotic protein targeting system dedicated to the transmembrane translocation of folded proteins. Substrate proteins are directed to the Tat translocase by signal peptides bearing a conserved SRRxFLK 'twin-arginine' motif. In Escherichia coli, most of the 27 periplasmically located Tat substrates are cofactor-containing respiratory enzymes, and many of these harbour a molybdenum cofactor at their active site. Molybdenum cofactor-containing proteins are not exclusively located in the periplasm, however, with the major respiratory nitrate reductase (NarG) and the biotin sulfoxide reductase (BisC), for example, being located at the cytoplasmic side of the membrane. Interestingly, both NarG and Bisc contain 'N-tail' regions that bear some sequence similarity to twin-arginine signal peptides. In this work, we have examined the relationship between the non-exported N-tails and the Tat system. Using a sensitive genetic screen for Tat transport, variant N-tails were identified that displayed Tat transport activity. For the NarG 36-residue N-tail, six amino acid changes were needed to induce transport activity. However, these changes interfered with binding by the NarJ biosynthetic chaperone and impaired biosynthesis of the native enzyme. For the BisC 36-residue N-tail, only five amino acid substitutions were needed to restore Tat transport activity. These modifications also impaired in vivo BisC activity, but it was not possible to identify a biosynthetic chaperone for this enzyme. These data highlight an intimate genetic and evolutionary link between some non-exported redox enzymes and those transported across membranes by the Tat translocation system.
KW - BIOTIN SULFOXIDE REDUCTASE
KW - BACTERIAL 2-HYBRID SYSTEM
KW - TWIN-ARGININE TRANSLOCASE
KW - ESCHERICHIA-COLI
KW - PROTEIN TRANSLOCATION
KW - SALMONELLA-TYPHIMURIUM
KW - NITRATE REDUCTASES
KW - CHAPERONE
KW - PATHWAY
KW - GENE
U2 - 10.1099/mic.0.033647-0
DO - 10.1099/mic.0.033647-0
M3 - Article
C2 - 19778964
SN - 1350-0872
VL - 155
SP - 3992
EP - 4004
JO - Microbiology
JF - Microbiology
IS - 12
ER -