Kinetic Analysis of the Assembly of the Outer Membrane Protein LamB in Escherichia coli Mutants Each Lacking a Secretion or Targeting Factor in a Different Cellular Compartment

• DOI: 10.1128/jb.01103-06
• Publication Date: 2006-12-28T23:08:11Z
• Authors: Alejandro R. Ureta; Robert G. Endres; Ned S. Wingreen; Thomas J. Silhavy
• Keywords: Inner membrane; Cell envelope; Cell membrane

ABSTRACT Outer membrane β-barrel proteins in gram-negative bacteria, such as Escherichia coli , must be translocated from their site of synthesis the cytoplasm to periplasm and finally delivered outer membrane. At least a dozen located cytoplasm, periplasm, both inner membranes are required catalyze this complex assembly process. normal growth temperatures conditions transport processes so fast that intermediates cannot detected. Using cells grown at low temperature slow process pulse-chase analysis with immunodetection methods, we followed newly synthesized LamB molecules during transit through cell envelope. The quality reproducibility data allowed us calculate rate constants for three different subassembly reactions. This kinetic revealed secB secD mutants exhibit nearly identical defects precursor translocation cytoplasm. However, subsequent reaction rates provided no clear evidence an additional role SecD assembly. Moreover, found surA qualitatively indistinguishable yfgL mutants, suggesting products these genes share common function process, most likely delivery YaeT