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Functional characterization of a microbial aquaglyceroporin
Alexandrine Froger1, Jean-Paul Rolland1, Patrick Bron1
1UMR CNRS, Interactions Cellulaires et Moléculaires, Equipe Canaux et Récepteurs Membranaires, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex, France1.
Abstract:
The major intrinsic proteins (MIPs) constitute a widespread membrane channel family essential for osmotic cell equilibrium. The MIPs can be classified into three functional subgroups: aquaporins, glycerol facilitators and aquaglyceroporins. Bacterial MIP genes have been identified in archaea as well as in Gram-positive and Gram-negative eubacteria. However, with the exception of Escherichia coli, most bacterial MIPs have been analysed by sequence homology. Since no MIP has yet been functionally characterized in Gram-positive bacteria, we have studied one of these members from Lactococcus lactis. This MIP is shown to be permeable to glycerol, like E. coli GlpF, and to water, like E. coli AqpZ. This is the first characterization of a microbial MIP that has a mixed function. This result provides important insights to reconstruct the evolutionary history of the MIP family and to elucidate the molecular pathway of water and other solutes in these channels.
Insights
This study characterizes a novel microbial major intrinsic protein (MIP) from Lactococcus lactis. This bifunctional channel facilitates both water and glycerol transport, offering evolutionary insights into MIPs.
Area of Science:
- Membrane Biology
- Microbiology
- Biochemistry
Background:
- Major intrinsic proteins (MIPs) form essential membrane channels for osmotic balance.
- MIPs are categorized into aquaporins, glycerol facilitators, and aquaglyceroporins.
- Bacterial MIP genes are found across archaea and eubacteria, but functional studies in Gram-positive bacteria are scarce.
Purpose of the Study:
- To functionally characterize a MIP from the Gram-positive bacterium Lactococcus lactis.
- To investigate the transport capabilities of this microbial MIP.
- To gain insights into the evolution and function of the MIP family.
Main Methods:
- Sequence homology analysis of bacterial MIP genes.
- Functional characterization of the Lactococcus lactis MIP.
- Transport assays for water and glycerol.
Main Results:
- The Lactococcus lactis MIP exhibits dual permeability to both water and glycerol.
- This bifunctional transport is analogous to Escherichia coli's AqpZ (water) and GlpF (glycerol).
- This marks the first functional characterization of a mixed-function microbial MIP.
Conclusions:
- The Lactococcus lactis MIP is a bifunctional channel, transporting both water and glycerol.
- This finding provides crucial data for understanding MIP evolution and solute transport pathways.
- Highlights the diverse functional roles of MIPs in microbial systems.