Transmembrane α-Helix Interactions are Required for the Functional Assembly of theEscherichia coliTol Complex

Lazzaroni, Jean-Claude; Vianney, Anne; Popot, Jean Luc; Bénédetti, Hélène; Samatey, Fadel A.; Lazdunski, Claude; Portalier, Raymond; Géli, Vincent

doi:10.1006/jmbi.1994.0058

Cited by 91 publications

(110 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This and secondary structure predictions suggest that this C-terminal segment may form a globular structure, with hydrophilic residues at the surface and hydrophobic residues buried in the three-dimensional structure. This structure may form a plug into the putative TolQR ion channel, since it is protected from the action of carboxypeptidase (11), and suppressive mutation of the TolQ TMH3 A177V mutant has been previously mapped into this segment (T139M, respectively) (11). In this region, many positions displayed a different pattern of labeling in response to proton-motive force and ion pathway residues (see below), suggesting that this segment undergoes structural modifications during the energy-converting process.…”

Section: Discussionmentioning

confidence: 99%

“…This large domain, subdivided in central (called TolR-2) and C-terminal (called TolR-3) domains, is required for TolR dimerization (9). TolQ and TolR proteins interact in the membrane through their TMHs in a 4:2 stoichiometry (4,9,10,11,12,13). It has been proposed that ion or proton flow at the interface of the TMHs of the TolQR complex regulates structural modifications within this complex and hence results in a conformational change within TolA (3)(4)(5).…”

mentioning

confidence: 99%

“…This latter domain has been shown to co-fractionate with membranes when produced in the periplasm of wild-type (WT) cells (9). Furthermore, suppressive mutations of nonfunctional TolQ TMH3 mutants have been isolated in this domain (5,11). In the work reported here, we have used residue substitutions with cysteines, oxidative cross-linking, and cysteine accessibilities to assess the role of the TolR C-terminal domain.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Movements of the TolR C-terminal Domain Depend on TolQR Ionizable Key Residues and Regulate Activity of the Tol Complex

Goemaere

Devert

Lloubès

et al. 2007

Journal of Biological Chemistry

View full text Add to dashboard Cite

The TolQRA proteins of Escherichia coli form an inner membrane complex involved in the maintenance of the outer membrane stability and in the late stages of cell division. The TolQR complex uses the proton-motive force to regulate TolA conformation and its interaction with the outer membrane Pal lipoprotein. It has been proposed that an ion channel forms at the TolQR transmembrane helix interface. This complex assembles with a minimal TolQ/TolR ratio of 4:2, therefore involving at least 14 transmembrane helices, which may form the ion pathway. The C-terminal periplasmic domain of TolR protein interacts with TolQ and has been proposed to control the TolQR channel activity. Here, we constructed unique cysteine substitutions in the last 27 residues of TolR. Each of the substitutions results in a functional TolR protein. Disulfide cross-linking demonstrates that the TolQR complex is dynamic, involving conformational modifications of TolR C-terminal domain. We monitored these structural changes by cysteine accessibility experiments and showed that the conformation of this domain is responsive to the proton-motive force and on the presence of critical residues of the ion pathway.

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Movements of the TolR C-terminal Domain Depend on TolQR Ionizable Key Residues and Regulate Activity of the Tol Complex

Goemaere

Devert

Lloubès

et al. 2007

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…This phenomenon of pseudoreversion has recently gained popularity as a means of identifying residues important to protein function (Dunn et al, 1988;Li & Baltimore, 1990;Supek et al, 1994;Anand et al, 1995;Lazzaroni et al, 1995). Yet, the structural bases by which second-site mutations restore function remain, for the most part, mysterious.…”

mentioning

confidence: 99%

Second‐site suppression of regulatory phosphorylation in Escherichia coli isocitrate dehydrogenase

et al. 1996

View full text Add to dashboard Cite

Inactivation of Escherichia coli isocitrate dehydrogenase upon phosphorylation at S113 depends upon the direct electrostatic repulsion of the negatively charged y-carboxylate of isocitrate by the negatively charged phosphoserine.The effect is mimicked by replacing S113 with aspartate or glutamate, which reduce performance (kcor/Ki.isocitrat/ K,.,,,,)by a factor of 10'. Here, we demonstrate that the inactivating effects of the electrostatic repulsion are completely eliminated by a second-site mutation, and provide the structural basis for this striking example of intragenic suppression. N115 is adjacent to S113 on one face of the D-helix, interacts with isocitrate and NADP+, and has been postulated to serve in both substrate binding and in catalysis. The single N115L substitution reduces affinity for isocitrate by a factor of 50 and performance by a factor of 500. However, the Nl15L substitution completely suppresses the inactivating electrostatic effects of S113D or S113E: the performance of the double mutants is lo5 higher than the S113D and S113E single mutants. These mutations have little effect on the kinetics of alternative substrates, which lack the charged y-carboxylate of isocitrate. Both glutamate and aspartate at site 113 remain fully ionized in the presence of leucine. In the crystal structure of the N115L mutant, the leucine adopts a different conformer from the wild-type asparagine. Repacking around the leucine forces the amino-terminus of the D-helix away from the rest of the active site. The hydrogen bond between E l 13 and N115 in the S113E single mutant is broken in the S113EIN115L mutant, allowing the glutamate side chain to move away from the y-carboxylate of isocitrate. These movements increase the distance between the carboxylates, diminish the electrostatic repulsion, and lead to the remarkably high activity of the S113E/N115L mutant.

show abstract

“…Isolation of suppressive mutations also brought information on heterodimer formation. Suppressive mutations of the non-functional TolQ mutants, A177V (TMH3) (43) or T145A (TMH2), were identified in the TolR anchor, whereas a suppressive mutation of the TolR D23A mutant was isolated in TolQ TMH3 (18 (16,47). These latter studies also identified MotA TMH residues that face each other.…”

Section: Discussionmentioning

confidence: 94%

Mapping the Interactions between Escherichia coli TolQ Transmembrane Segments

Zhang

Goemaere

Seddiki

et al. 2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

Transmembrane α-Helix Interactions are Required for the Functional Assembly of theEscherichia coliTol Complex

Cited by 91 publications

References 39 publications

Movements of the TolR C-terminal Domain Depend on TolQR Ionizable Key Residues and Regulate Activity of the Tol Complex

Movements of the TolR C-terminal Domain Depend on TolQR Ionizable Key Residues and Regulate Activity of the Tol Complex

Second‐site suppression of regulatory phosphorylation in Escherichia coli isocitrate dehydrogenase

Mapping the Interactions between Escherichia coli TolQ Transmembrane Segments

Contact Info

Product

Resources

About