Complexes between protein export chaperone SecB and SecA. Evidence for separate sites on SecA providing binding energy and regulatory interactions.
During localization to the periplasmic space or to the outer membrane of Escherichia coli some proteins are dependent on binding to the cytosolic chaperone SecB, which in turn is targeted to the membrane by specific interaction with SecA, a peripheral component of the translocase. Five variant forms of SecB, previously demonstrated to be defective in mediating export in vivo (Gannon, P. M., and Kumamoto, C. A. (1993) J. Biol. Chem. 268, 1590-1595; Kimsey, H. K., Dagarag, M. D., and Kumamoto, C. A. (1995) J. Biol. Chem. 270, 22831-22835) were investigated with respect to their ability to bind SecA both in solution and at the membrane translocase. We present evidence that at least two regions of SecA are involved in the formation of active complexes with SecB. The variant forms of SecB were all capable of interacting with SecA in solution to form complexes with stability similar to that of complexes between SecA and wild-type SecB. However, the variant forms were defective in interaction with a separate region of SecA, which was shown to trigger a change that was correlated to activation of the complex. The region of SecA involved in activation of the complexes was defined as the extreme carboxyl-terminal 21 aminoacyl residues.
Woodbury
R L
RL
School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, USA.
Topping
T B
TB
Diamond
D L
DL
Suciu
D
D
Kumamoto
C A
CA
Hardy
S J
SJ
Randall
L L
LL
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D001692:Biological Transport; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000378:metabolism*; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D014644:Genetic Variation; D008024:Ligands; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D033902:Periplasmic Binding Proteins; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D020836:Protein Structure, Quaternary; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013816:Thermodynamics
D001426:Bacterial Proteins; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; D009004:Monosaccharide Transport Proteins; D010446:Peptide Fragments; D033902:Periplasmic Binding Proteins; D011498:Protein Precursors; D000069816:SEC Translocation Channels; C057842:SecB protein, Bacteria; C023550:galactose-binding protein; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins