Constraints on models for the flagellar rotary motor

Berg, Howard C.

doi:10.1098/rstb.2000.0590

Cited by 68 publications

(73 citation statements)

References 126 publications

(132 reference statements)

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“…Recent data suggest that the motor complex may have a larger structure than previously assumed or that the minimal forcegenerating unit is not a 4:2 complex (46). Presently, however, we do not know the mechanism of generation of rotational force, although many models have been presented (8,10,41). We anticipate that our present data will assist in the understanding of the mechanism once high-resolution data on the stator complex are available.…”

Section: Discussionmentioning

confidence: 90%

Concerted Effects of Amino Acid Substitutions in Conserved Charged Residues and Other Residues in the Cytoplasmic Domain of PomA, a Stator Component of Na ⁺ -Driven Flagella

2004

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PomA is a membrane protein that is one of the essential components of the sodium-driven flagellar motor in Vibrio species. The cytoplasmic charged residues of Escherichia coli MotA, which is a PomA homolog, are believed to be required for the interaction of MotA with the C-terminal region of FliG. It was previously shown that a PomA variant with neutral substitutions in the conserved charged residues (R88A, K89A, E96Q, E97Q, and E99Q; AAQQQ) was functional. In the present study, five other conserved charged residues were replaced with neutral amino acids in the AAQQQ PomA protein. These additional substitutions did not affect the function of PomA. However, strains expressing the AAQQQ PomA variant with either an L131F or a T132M substitution, neither of which affected motor function alone, exhibited a temperature-sensitive (TS) motility phenotype. The double substitutions R88A or E96Q together with L131F were sufficient for the TS phenotype. The motility of the PomA TS mutants immediately ceased upon a temperature shift from 20 to 42°C and was restored to the original level approximately 10 min after the temperature was returned to 20°C. It is believed that PomA forms a channel complex with PomB. The complex formation of TS PomA and PomB did not seem to be affected by temperature. Suppressor mutations of the TS phenotype were mapped in the cytoplasmic boundaries of the transmembrane segments of PomA. We suggest that the cytoplasmic surface of PomA is changed by the amino acid substitutions and that the interaction of this surface with the FliG C-terminal region is temperature sensitive.

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Section: Discussionmentioning

confidence: 90%

Concerted Effects of Amino Acid Substitutions in Conserved Charged Residues and Other Residues in the Cytoplasmic Domain of PomA, a Stator Component of Na ⁺ -Driven Flagella

2004

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“…The bacterial flagellar motor, which is embedded within the cytoplasmic membrane, is a rotary machine to generate motility (1,15). The motor is placed in either of two states, counterclockwise rotation and clockwise rotation, which cause swimming and tumbling, respectively.…”

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confidence: 99%

Effect of Intracellular pH on Rotational Speed of Bacterial Flagellar Motors

Imae²,

et al. 2003

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Weak acids such as acetate and benzoate, which partially collapse the transmembrane proton gradient, not only mediate pH taxis but also impair the motility of Escherichia coli and Salmonella at an external pH of 5.5. In this study, we examined in more detail the effect of weak acids on motility at various external pH values. A change of external pH over the range 5.0 to 7.8 hardly affected the swimming speed of E. coli cells in the absence of 34 mM potassium acetate. In contrast, the cells decreased their swimming speed significantly as external pH was shifted from pH 7.0 to 5.0 in the presence of 34 mM acetate. The total proton motive force of E. coli cells was not changed greatly by the presence of acetate. We measured the rotational rate of tethered E. coli cells as a function of external pH. Rotational speed decreased rapidly as the external pH was decreased, and at pH 5.0, the motor stopped completely. When the external pH was returned to 7.0, the motor restarted rotating at almost its original level, indicating that high intracellular proton (H ؉ ) concentration does not irreversibly abolish flagellar motor function. Both the swimming speeds and rotation rates of tethered cells of Salmonella also decreased considerably when the external pH was shifted from pH 7.0 to 5.5 in the presence of 20 mM benzoate. We propose that the increase in the intracellular proton concentration interferes with the release of protons from the torque-generating units, resulting in slowing or stopping of the motors.The bacterial flagellar motor, which is embedded within the cytoplasmic membrane, is a rotary machine to generate motility (1, 15). The motor is placed in either of two states, counterclockwise rotation and clockwise rotation, which cause swimming and tumbling, respectively. The switch in the direction of flagellar motor rotation is the basis of chemotaxis. In Escherichia coli and Salmonella, the motor is driven by the transmembrane electrochemical gradient of protons (H ϩ ), i.e., the proton motive force (17,18). Although many studies have been carried out, it still remains unknown how the motors convert the proton influx into the energy for generating torque.Based on genetic analyses of mutants with paralyzed phenotypes, five proteins are known to be responsible for torque generation in the flagellar motor: MotA, MotB, FliG, FliM, and FliN. MotA and MotB are cytoplasmic membrane proteins and together form a complex. The MotA/MotB complex is responsible for proton conductance and functions as a torquegenerating unit (2, 3). Since MotB is postulated to be anchored to the peptidoglycan layer, the complex could be the stator (4). FliG, FliM, and FliN are involved in torque generation and switching of the direction of flagellar motor rotation (7, 29). They form the C ring, which is directly mounted onto the cytoplasmic side of the flagellar MS ring and therefore seems likely to be the rotor (6, 23). It has been suggested that electrostatic interactions at the rotor-stator interface are important for torque generation (31)...

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“…The structures in these size ranges pose several interesting questions for example how does the flagellar motor of E Coli run? [5,6] or how do electrons move through organometallic nanowires [7]. It is also challenging to make materials on this scale as it is easier to synthesize molecules on a large scale and characterize them.…”

Section: Introductionmentioning

confidence: 99%

Silicon Based Nanocoatings on Metal Alloys and Their Role in Surface Engineering

Bhure¹,

Mahapatro

2010

Silicon

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Metals and their alloys have been widely used in all aspects of science and engineering. However the science of nanotechnology is driving newer demands and requirements for better performance of existing materials and also at a higher level of precision. This is naturally presenting complicated demands on the surface of these metals with a need for surface modification. Self Assembled Monolayers (SAMs) are nanosized coatings that present the most efficient method of carrying out surface modification. Alkylsilanes are silicon based SAMs which are compatible with the majority of metals and alloys. These nanocoatings can serve primary functions such as surface coverage, etch protection and anti corrosion, along with a host of other secondary chemical functions because of their amphiphilic nature. We present a brief introduction to surface modification of metals and alloys followed by a detailed description of silane based nanocoatings and their applications in technology. Then a look at the engineering aspects of these coatings in terms of patterning techniques is presented along with a discussion of the applications of patterned SAMs.

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Constraints on models for the flagellar rotary motor

Cited by 68 publications

References 126 publications

Concerted Effects of Amino Acid Substitutions in Conserved Charged Residues and Other Residues in the Cytoplasmic Domain of PomA, a Stator Component of Na ⁺ -Driven Flagella

Concerted Effects of Amino Acid Substitutions in Conserved Charged Residues and Other Residues in the Cytoplasmic Domain of PomA, a Stator Component of Na ⁺ -Driven Flagella

Effect of Intracellular pH on Rotational Speed of Bacterial Flagellar Motors

Silicon Based Nanocoatings on Metal Alloys and Their Role in Surface Engineering

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Constraints on models for the flagellar rotary motor

Cited by 68 publications

References 126 publications

Concerted Effects of Amino Acid Substitutions in Conserved Charged Residues and Other Residues in the Cytoplasmic Domain of PomA, a Stator Component of Na + -Driven Flagella

Concerted Effects of Amino Acid Substitutions in Conserved Charged Residues and Other Residues in the Cytoplasmic Domain of PomA, a Stator Component of Na + -Driven Flagella

Effect of Intracellular pH on Rotational Speed of Bacterial Flagellar Motors

Silicon Based Nanocoatings on Metal Alloys and Their Role in Surface Engineering

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Product

Resources

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Concerted Effects of Amino Acid Substitutions in Conserved Charged Residues and Other Residues in the Cytoplasmic Domain of PomA, a Stator Component of Na ⁺ -Driven Flagella

Concerted Effects of Amino Acid Substitutions in Conserved Charged Residues and Other Residues in the Cytoplasmic Domain of PomA, a Stator Component of Na ⁺ -Driven Flagella