Dataset Information

Genetic screen for potassium leaky small mechanosensitive channels (MscS) in Escherichia coli: recognition of cytoplasmic ? domain as a new gating element.

ABSTRACT: Mechanosensitive membrane channels in bacteria respond to the mechanical stretching of the membrane. They will open when bacteria are subjected to rapid osmotic down shock. MscS is a bacterial mechanosensitive channel of small conductance. It is a heptameric membrane protein whose transmembrane part, including the gate and its kinetics, has been well characterized. MscS has a large cytoplasmic domain of a cage-like shape that changes its conformation upon gating, but its involvement in gating is not understood. We screened MscS for mutations that cause potassium leak in Escherichia coli strains deficient in potassium transport systems. We did a phenotypic analysis of single and multiple mutants and recorded the single channel activities of some of them. After these analyses, we attributed the effects of a number of mutations to particular functional states of the channel. Our screen revealed that MscS leaks potassium in a desensitized and in an inactivated state. It also appeared that the lower part of TM3 (transmembrane, pore-forming helix) and the cytoplasmic ? domain are tightly packed in the inactivated state but are dissociated in the open state. We attribute the TM3-? interaction to stabilization of the inactivated state in MscS and to the control of tight closure of its membrane pore.

SUBMITTER: Koprowski P

PROVIDER: S-EPMC3013047 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Genetic screen for potassium leaky small mechanosensitive channels (MscS) in Escherichia coli: recognition of cytoplasmic β domain as a new gating element.

Koprowski Piotr P Grajkowski Wojciech W Isacoff Ehud Y EY Kubalski Andrzej A

The Journal of biological chemistry 20101026 1

Mechanosensitive membrane channels in bacteria respond to the mechanical stretching of the membrane. They will open when bacteria are subjected to rapid osmotic down shock. MscS is a bacterial mechanosensitive channel of small conductance. It is a heptameric membrane protein whose transmembrane part, including the gate and its kinetics, has been well characterized. MscS has a large cytoplasmic domain of a cage-like shape that changes its conformation upon gating, but its involvement in gating is ...[more]

PMID: 20978126

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Project description:The mechanosensitive channel of large conductance (MscL) is capable of transducing mechanical stimuli such as membrane tension into an electrochemical response. MscL provides a widely-studied model system for mechanotransduction and, more generally, for how bilayer mechanical properties regulate protein conformational changes. Much effort has been expended on the detailed experimental characterization of the molecular structure and biological function of MscL. However, despite its central significance, even basic issues such as the physiologically relevant oligomeric states and molecular structures of MscL remain a matter of debate. In particular, tetrameric, pentameric, and hexameric oligomeric states of MscL have been proposed, together with a range of detailed molecular structures of MscL in the closed and open channel states. Previous theoretical work has shown that the basic phenomenology of MscL gating can be understood using an elastic model describing the energetic cost of the thickness deformations induced by MscL in the surrounding lipid bilayer. Here, we generalize this elastic model to account for the proposed oligomeric states and hydrophobic shapes of MscL. We find that the oligomeric state and hydrophobic shape of MscL are reflected in the energetic cost of lipid bilayer deformations. We make quantitative predictions pertaining to the gating characteristics associated with various structural models of MscL and, in particular, show that different oligomeric states and hydrophobic shapes of MscL yield distinct membrane contributions to the gating energy and gating tension. Thus, the functional properties of MscL provide a signature of the oligomeric state and hydrophobic shape of MscL. Our results suggest that, in addition to the hydrophobic mismatch between membrane proteins and the surrounding lipid bilayer, the symmetry and shape of the hydrophobic surfaces of membrane proteins play an important role in the regulation of protein function by bilayer membranes.

Dataset Information

Genetic screen for potassium leaky small mechanosensitive channels (MscS) in Escherichia coli: recognition of cytoplasmic ? domain as a new gating element.

Publications

Genetic screen for potassium leaky small mechanosensitive channels (MscS) in Escherichia coli: recognition of cytoplasmic β domain as a new gating element.

Similar Datasets

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