Structural organization of the twin-arginine translocation system in Streptomyces lividans.
The twin-arginine translocation (Tat) system exports folded proteins across bacterial cytoplasmic membranes. Recently, genes encoding TatA, TatB and TatC homologues were identified in Streptomyces lividans and the functionality of the Tat pathway was demonstrated. Here, we have examined the localization and structural organization of the Tat components in S. lividans. Interestingly, besides being membrane-associated proteins, S. lividans TatA and TatB were also detected in the cytoplasm. TatC could only be detected in isolated membrane fractions. Whereas all TatC was found to be stably inserted in the membrane, part of membrane-associated TatA and TatB could be extracted following high salt, sodium carbonate or urea treatment suggesting a more loose association with the membrane. Finally, we have analyzed Tat complexes that could be purified from an S. lividans TatABC overproducing strain. From the cytoplasmic membrane, two types of high molecular mass Tat complexes could be isolated having a similar composition as those isolated from Escherichia coli. In the cytoplasm, TatA and TatB were detected as monomer or as homo-oligomeric complexes.
De Keersmaeker
Sophie
S
Laboratory of Bacteriology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium. Sophie.Dekeersmaeker@rega.kuleuven.ac.be
Van Mellaert
Lieve
L
Schaerlaekens
Kristien
K
Van Dessel
Wesley
W
Vrancken
Kristof
K
Lammertyn
Elke
E
Anné
Jozef
J
Geukens
Nick
N
D001120:Arginine / Q000378:metabolism*; D001483:Base Sequence; D015153:Blotting, Western; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D048170:Streptomyces lividans / Q000378:metabolism*
D017931:DNA Primers; D026901:Membrane Transport Proteins; D001120:Arginine