Establishment of a Protein Concentration Gradient in the Outer Membrane Requires Two Diffusion-Limiting Mechanisms
Por:
David Ginez, Luis, Osorio, Aurora, Camarena, Laura, Poggio, Sebastian
Publicada:
1 sep 2019
Resumen:
OmpA-like proteins are involved in the stabilization of the outer
membrane, resistance to osmotic stress, and pathogenesis. In Caulobacter
crescentus, OmpA2 forms a physiologically relevant concentration
gradient that forms by an uncharacterized mechanism, in which the
gradient orientation depends on the position of the gene locus. This
suggests that OmpA2 is synthesized and translocated to the periplasm
close to the position of the gene and that the gradient forms by
diffusion of the protein from this point. To further understand how the
OmpA2 gradient is established, we determined the localization and
mobility of the full protein and of its two structural domains. We show
that OmpA2 does not diffuse and that both domains are required for
gradient formation. The C-terminal domain binds tightly to the cell wall
and the immobility of the full protein depends on the binding of this
domain to the peptidoglycan; in contrast, the N-terminal membrane
beta-barrel diffuses slowly. Our results support a model in which once
OmpA2 is translocated to the periplasm, the N-terminal membrane
beta-barrel is required for an initial fast restriction of diffusion
until the position of the protein is stabilized by the binding of the
C-terminal domain to the cell wall. The implications of these results on
outer membrane protein diffusion and organization are discussed.
IMPORTANCE Protein concentration gradients play a relevant role in the
organization of the bacterial cell. The Caulobacter crescentus protein
OmpA2 forms an outer membrane polar concentration gradient. To
understand the molecular mechanism that determines the formation of this
gradient, we characterized the mobility and localization of the full
protein and of its two structural domains an integral outer membrane
beta-barrel and a periplasmic peptidoglycan binding domain. Each domain
has a different role in the formation of the OmpA2 gradient, which
occurs in two steps. We also show that the OmpA2 outer membrane
beta-barrel can diffuse, which is in contrast to what has been reported
previously for several integral outer membrane proteins in Escherichia
coli, suggesting a different organization of the outer membrane
proteins.
Filiaciones:
David Ginez, Luis:
Univ Nacl Autonoma Mexico, Inst Invest Biomed, Mexico City, DF, Mexico
Osorio, Aurora:
Univ Nacl Autonoma Mexico, Inst Invest Biomed, Mexico City, DF, Mexico
Camarena, Laura:
Univ Nacl Autonoma Mexico, Inst Invest Biomed, Mexico City, DF, Mexico
Poggio, Sebastian:
Univ Nacl Autonoma Mexico, Inst Invest Biomed, Mexico City, DF, Mexico
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