Dataset Information

Crystal structure of the cell wall anchor domain of MotB, a stator component of the bacterial flagellar motor: implications for peptidoglycan recognition.

ABSTRACT: The stator ring of the bacterial flagellar motor is composed of the MotA and MotB proteins that act together to generate a turning force (torque) acting on the FliG ring of the rotor. The C-terminal domain of MotB (MotB-C) is believed to anchor the MotA/MotB complex to peptidoglycan (PG) of the cell wall. The first crystal structures of MotB-C and its complex with N-acetylmuramic acid (NAM) have been determined to 1.6- and 2.3-A resolution, respectively. MotB-C is a dimer, both in solution and in the crystal. The two glycan chains of the PG ligand can be modeled as semirigid helices and docked into the grooves harboring the NAM molecules on the opposite faces of the dimer. The model suggests that a concave hydrophilic surface created upon edge-to-edge beta-sheet dimerization and centered around the 2-fold axis of the dimer can accommodate the peptide cross-bridge linking the two sugar chains. Significant structural similarities were found between MotB-C and the PG-binding domains of reduction-modifiable protein M and peptidoglycan-associated lipoprotein exclude, suggesting that PG recognition by different outer membrane protein A-like proteins may be governed by very similar molecular mechanisms that evidently involve protein dimerization.

SUBMITTER: Roujeinikova A

PROVIDER: S-EPMC2492448 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature

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Crystal structure of the cell wall anchor domain of MotB, a stator component of the bacterial flagellar motor: implications for peptidoglycan recognition.

Roujeinikova Anna A

Proceedings of the National Academy of Sciences of the United States of America 20080722 30

The stator ring of the bacterial flagellar motor is composed of the MotA and MotB proteins that act together to generate a turning force (torque) acting on the FliG ring of the rotor. The C-terminal domain of MotB (MotB-C) is believed to anchor the MotA/MotB complex to peptidoglycan (PG) of the cell wall. The first crystal structures of MotB-C and its complex with N-acetylmuramic acid (NAM) have been determined to 1.6- and 2.3-A resolution, respectively. MotB-C is a dimer, both in solution and i ...[more]

PMID: 18647830

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Project description:The bacterial flagellum is the motility organelle powered by a rotary motor. The rotor and stator elements of the motor are located in the cytoplasmic membrane and cytoplasm. The stator units assemble around the rotor, and an ion flux (typically H+ or Na+) conducted through a channel of the stator induces conformational changes that generate rotor torque. Electrostatic interactions between the stator protein PomA in Vibrio (MotA in Escherichia coli) and the rotor protein FliG have been shown by genetic analyses, but have not been demonstrated biochemically. Here, we used site-directed photo- and disulfide-crosslinking to provide direct evidence for the interaction. We introduced a UV-reactive amino acid, p-benzoyl-L-phenylalanine (pBPA), into the cytoplasmic region of PomA or the C-terminal region of FliG in intact cells. After UV irradiation, pBPA inserted at a number of positions in PomA formed a crosslink with FliG. PomA residue K89 gave the highest yield of crosslinks, suggesting that it is the PomA residue nearest to FliG. UV-induced crosslinking stopped motor rotation, and the isolated hook-basal body contained the crosslinked products. pBPA inserted to replace residues R281 or D288 in FliG formed crosslinks with the Escherichia coli stator protein, MotA. A cysteine residue introduced in place of PomA K89 formed disulfide crosslinks with cysteine inserted in place of FliG residues R281 and D288, and some other flanking positions. These results provide the first demonstration of direct physical interaction between specific residues in FliG and PomA/MotA.ImportanceThe bacterial flagellum is a unique organelle that functions as a rotary motor. The interaction between the stator and rotor is indispensable for stator assembly into the motor and the generation of motor torque. However, the interface of the stator-rotor interaction has only been defined by mutational analysis. Here, we detected the stator-rotor interaction using site-directed photo- and disulfide-crosslinking approaches. We identified several residues in the PomA stator, especially K89, that are in close proximity to the rotor. Moreover, we identified several pairs of stator and rotor residues that interact. This study directly demonstrates the nature of the stator-rotor interaction and suggests how stator units assemble around the rotor and generate torque in the bacterial flagellar motor.

Dataset Information

Crystal structure of the cell wall anchor domain of MotB, a stator component of the bacterial flagellar motor: implications for peptidoglycan recognition.

Publications

Crystal structure of the cell wall anchor domain of MotB, a stator component of the bacterial flagellar motor: implications for peptidoglycan recognition.

Similar Datasets

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