Hydrophilicity of a single residue within MscL correlates with increased channel mechanosensitivity

Kenjiro Yoshimura, Ann Batiza, Matt Schroeder, Paul Blount, Ching Kung

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Abstract

Mechanosensitive channel large (MscL) encodes the large conductance mechanosensitive channel of the Escherichia coli inner membrane that protects bacteria from lysis upon osmotic shock. To elucidate the molecular mechanism of MscL gating, we have comprehensively substituted Gly22 with all other common amino acids. Gly22 was highlighted in random mutagenesis screens of E. coli MscL (Ou et al., 1998, Proc. Nat. Acad. Sci. USA. 95:11471-11475). By analogy to the recently published MscL structure from Mycobacterium tuberculosis (Chang et al., 1998, Science. 282:2220-2226), Gly22 is buried within the constriction that closes the pore. Substituting Gly22 with hydrophilic residues decreased the threshold pressure at which channels opened and uncovered an intermediate subconducting state. In contrast, hydrophobic substitutions increased the threshold pressure. Although hydrophobic substitutions had no effect on growth, similar to the effect of an MscL deletion, channel hyperactivity caused by hydrophilic substitutions correlated with decreased proliferation. These results suggest a model for gating in which Gly22 moves from a hydrophobic, and through a hydrophilic, environment upon transition from the closed to open conformation.

Original languageEnglish (US)
Pages (from-to)1960-1972
Number of pages13
JournalBiophysical Journal
Volume77
Issue number4
StatePublished - Oct 1999

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Hydrophobic and Hydrophilic Interactions
Escherichia coli
Pressure
Osmotic Pressure
Mycobacterium tuberculosis
Constriction
Mutagenesis
Bacteria
Amino Acids
Membranes
Growth

ASJC Scopus subject areas

  • Biophysics

Cite this

Hydrophilicity of a single residue within MscL correlates with increased channel mechanosensitivity. / Yoshimura, Kenjiro; Batiza, Ann; Schroeder, Matt; Blount, Paul; Kung, Ching.

In: Biophysical Journal, Vol. 77, No. 4, 10.1999, p. 1960-1972.

Research output: Contribution to journalArticle

Yoshimura, K, Batiza, A, Schroeder, M, Blount, P & Kung, C 1999, 'Hydrophilicity of a single residue within MscL correlates with increased channel mechanosensitivity', Biophysical Journal, vol. 77, no. 4, pp. 1960-1972.
Yoshimura, Kenjiro ; Batiza, Ann ; Schroeder, Matt ; Blount, Paul ; Kung, Ching. / Hydrophilicity of a single residue within MscL correlates with increased channel mechanosensitivity. In: Biophysical Journal. 1999 ; Vol. 77, No. 4. pp. 1960-1972.
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