The envelope of Gram-negative bacteria consists of two membranes separated by the periplasmic compartment that contains the peptidoglycan wall. The inner membrane (IM) is in contact with the cytosol while the outer membrane (OM) contacts the extracellular environment. The OM is a unique structure, essential for Gram-negative bacteria, composed of lipopolysaccharide (LPS), phospholipids and proteins. It is a very selective permeability barrier that allows the bacteria to survive in hostile environments such as the gut, where the OM resistance to bile salts allows enteric bacteria to thrive. The components of the OM are the first to come in contact with a host upon infection and strongly modulate the interaction of symbiotic and pathogenic bacteria with their host. A clear understanding of the OM biogenesis process is essential to understand host? pathogen interactions as well as a fundamental aspect of bacterial physiology. Outer membrane proteins (OMPs) are integral membrane proteins with b-barrel structures embedded in the OM. Many OMPs are immunogenic and some of them serve as adhesins mediating adhesion and colonization of host tissues. OMPs are synthesized in the cytosol and translocated across the IM by the Sec translocation machinery and inserted specifically in the outer membrane by a multiprotein complex known as b-Barrel Assembly Machine (BAM). However, the molecular mechanisms by which OMPs are targeted to the OM and inserted by BAM are poorly understood. In this proposal, we will define the fundamentals of OMP transport and assembly focusing on the BAM complex. We will (i) define the mechanism of OMP targeting to the OM and (ii) test mechanistic hypotheses of OMP insertion derived from the high- resolution structures of BAM.

Public Health Relevance

This application seeks to understand fundamental aspects of the molecular mechanisms underlying outer membrane protein transport, folding and insertion in Gram negative bacteria. Understanding this process is crucial to develop and evaluate inhibitory compounds that would represent a novel class of antimicrobials. These would be analogous to beta-lactams, which are effective by interfering with cell wall synthesis.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM127462-02
Application #
9689486
Study Section
Prokaryotic Cell and Molecular Biology Study Section (PCMB)
Program Officer
Flicker, Paula F
Project Start
2018-05-01
Project End
2022-03-31
Budget Start
2019-04-01
Budget End
2020-03-31
Support Year
2
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of Colorado at Boulder
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
007431505
City
Boulder
State
CO
Country
United States
Zip Code
80303