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Sodium-driven energy conversion for flagellar rotation of the earliest divergent hyperthermophilic bacterium.

Takekawa N, Nishiyama M, Kaneseki T, Kanai T, Atomi H, Kojima S, Homma M - Sci Rep (2015)

Bottom Line: Here we observed that A. aeolicus has polar flagellum and can swim with a speed of 90 μm s(-1) at 85 °C.We expressed the A. aeolicus mot genes (motA and motB), which encode the torque generating stator proteins of the flagellar motor, in a corresponding mot nonmotile mutant of Escherichia coli.Using this system in E. coli, we demonstrate that the A. aeolicus motor is driven by Na(+).

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.

ABSTRACT
Aquifex aeolicus is a hyperthermophilic, hydrogen-oxidizing and carbon-fixing bacterium that can grow at temperatures up to 95 °C. A. aeolicus has an almost complete set of flagellar genes that are conserved in bacteria. Here we observed that A. aeolicus has polar flagellum and can swim with a speed of 90 μm s(-1) at 85 °C. We expressed the A. aeolicus mot genes (motA and motB), which encode the torque generating stator proteins of the flagellar motor, in a corresponding mot nonmotile mutant of Escherichia coli. Its motility was slightly recovered by expression of A. aeolicus MotA and chimeric MotB whose periplasmic region was replaced with that of E. coli. A point mutation in the A. aeolicus MotA cytoplasmic region remarkably enhanced the motility. Using this system in E. coli, we demonstrate that the A. aeolicus motor is driven by Na(+). As motor proteins from hyperthermophilic bacteria represent the earliest motor proteins in evolution, this study strongly suggests that ancient bacteria used Na(+) for energy coupling of the flagellar motor. The Na(+)-driven flagellar genes might have been laterally transferred from early-branched bacteria into late-branched bacteria and the interaction surfaces of the stator and rotor seem not to change in evolution.

No MeSH data available.


Related in: MedlinePlus

Schematic cartoon of the flagellum and the stator proteins.(A) The flagellum is a large complex composed of many proteins and consists of a filament, a hook and a basal body. A. aeolicus has most genes for flagellar component except for FliM. (B) The stator is composed of two membrane proteins, MotA (blue) and MotB (red). MotA is a four TM protein and MotB is single TM protein. The spontaneous mutated Alanine residue is indicated as ‘A’ in the black circle. Black arrowhead, border of chimeric MotB: OM, outer membrane; PG, peptidoglycan layer; IM, inner membrane.
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f1: Schematic cartoon of the flagellum and the stator proteins.(A) The flagellum is a large complex composed of many proteins and consists of a filament, a hook and a basal body. A. aeolicus has most genes for flagellar component except for FliM. (B) The stator is composed of two membrane proteins, MotA (blue) and MotB (red). MotA is a four TM protein and MotB is single TM protein. The spontaneous mutated Alanine residue is indicated as ‘A’ in the black circle. Black arrowhead, border of chimeric MotB: OM, outer membrane; PG, peptidoglycan layer; IM, inner membrane.

Mentions: The flagellum is an organelle conserved throughout a wide range of bacteria. The mechanisms involved in the assembly and function of flagellum are well studied in some bacteria such as Escherichia coli or Salmonella typhimurium. Each flagellum has a long helical structure that is about 10–15 μm long, and its assembly involves more than 50 different genes9. The flagellum works as a screw by rotation, and its energy source is the electrochemical potential difference between the inside and outside of the cell. The flagellar motor, which is located at the base of the flagellum, is composed of a rotor and stator. The stator is a membrane-embedded energy converter made of four MotA molecules and two MotB molecules1011 (Fig. 1A,B), and converts the ion influx through itself into the rotation of the rotor. MotA and MotB are a four TM protein and a single TM protein, respectively1213 (Figs 1B and S2). The third and fourth TM segments of MotA and the TM segment of MotB is thought to form an ion conductive pathway111415. The stator is separated into three parts in terms of function, i) a large periplasmic region which contains a Peptidoglycan (PG)-binding domain and changes its conformation dynamically to anchor to the PG layer to fix the stators around the rotor1617, ii) the plug and transmembrane (TM) region which regulates the ion conductivity and forms a selective ion channel1819, and iii) a large cytoplasmic region which is important for the assembly around the rotor and directly interacts with the rotor (FliG) to generate the rotational force202122.


Sodium-driven energy conversion for flagellar rotation of the earliest divergent hyperthermophilic bacterium.

Takekawa N, Nishiyama M, Kaneseki T, Kanai T, Atomi H, Kojima S, Homma M - Sci Rep (2015)

Schematic cartoon of the flagellum and the stator proteins.(A) The flagellum is a large complex composed of many proteins and consists of a filament, a hook and a basal body. A. aeolicus has most genes for flagellar component except for FliM. (B) The stator is composed of two membrane proteins, MotA (blue) and MotB (red). MotA is a four TM protein and MotB is single TM protein. The spontaneous mutated Alanine residue is indicated as ‘A’ in the black circle. Black arrowhead, border of chimeric MotB: OM, outer membrane; PG, peptidoglycan layer; IM, inner membrane.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525482&req=5

f1: Schematic cartoon of the flagellum and the stator proteins.(A) The flagellum is a large complex composed of many proteins and consists of a filament, a hook and a basal body. A. aeolicus has most genes for flagellar component except for FliM. (B) The stator is composed of two membrane proteins, MotA (blue) and MotB (red). MotA is a four TM protein and MotB is single TM protein. The spontaneous mutated Alanine residue is indicated as ‘A’ in the black circle. Black arrowhead, border of chimeric MotB: OM, outer membrane; PG, peptidoglycan layer; IM, inner membrane.
Mentions: The flagellum is an organelle conserved throughout a wide range of bacteria. The mechanisms involved in the assembly and function of flagellum are well studied in some bacteria such as Escherichia coli or Salmonella typhimurium. Each flagellum has a long helical structure that is about 10–15 μm long, and its assembly involves more than 50 different genes9. The flagellum works as a screw by rotation, and its energy source is the electrochemical potential difference between the inside and outside of the cell. The flagellar motor, which is located at the base of the flagellum, is composed of a rotor and stator. The stator is a membrane-embedded energy converter made of four MotA molecules and two MotB molecules1011 (Fig. 1A,B), and converts the ion influx through itself into the rotation of the rotor. MotA and MotB are a four TM protein and a single TM protein, respectively1213 (Figs 1B and S2). The third and fourth TM segments of MotA and the TM segment of MotB is thought to form an ion conductive pathway111415. The stator is separated into three parts in terms of function, i) a large periplasmic region which contains a Peptidoglycan (PG)-binding domain and changes its conformation dynamically to anchor to the PG layer to fix the stators around the rotor1617, ii) the plug and transmembrane (TM) region which regulates the ion conductivity and forms a selective ion channel1819, and iii) a large cytoplasmic region which is important for the assembly around the rotor and directly interacts with the rotor (FliG) to generate the rotational force202122.

Bottom Line: Here we observed that A. aeolicus has polar flagellum and can swim with a speed of 90 μm s(-1) at 85 °C.We expressed the A. aeolicus mot genes (motA and motB), which encode the torque generating stator proteins of the flagellar motor, in a corresponding mot nonmotile mutant of Escherichia coli.Using this system in E. coli, we demonstrate that the A. aeolicus motor is driven by Na(+).

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.

ABSTRACT
Aquifex aeolicus is a hyperthermophilic, hydrogen-oxidizing and carbon-fixing bacterium that can grow at temperatures up to 95 °C. A. aeolicus has an almost complete set of flagellar genes that are conserved in bacteria. Here we observed that A. aeolicus has polar flagellum and can swim with a speed of 90 μm s(-1) at 85 °C. We expressed the A. aeolicus mot genes (motA and motB), which encode the torque generating stator proteins of the flagellar motor, in a corresponding mot nonmotile mutant of Escherichia coli. Its motility was slightly recovered by expression of A. aeolicus MotA and chimeric MotB whose periplasmic region was replaced with that of E. coli. A point mutation in the A. aeolicus MotA cytoplasmic region remarkably enhanced the motility. Using this system in E. coli, we demonstrate that the A. aeolicus motor is driven by Na(+). As motor proteins from hyperthermophilic bacteria represent the earliest motor proteins in evolution, this study strongly suggests that ancient bacteria used Na(+) for energy coupling of the flagellar motor. The Na(+)-driven flagellar genes might have been laterally transferred from early-branched bacteria into late-branched bacteria and the interaction surfaces of the stator and rotor seem not to change in evolution.

No MeSH data available.


Related in: MedlinePlus