Structural Study of MPN387, an Essential Protein for Gliding Motility of a Human-Pathogenic Bacterium, Mycoplasma pneumoniae.
Mycoplasma pneumoniae is a human pathogen that glides on host cell surfaces with repeated catch and release of sialylated oligosaccharides. At a pole, this organism forms a protrusion called the attachment organelle, which is composed of surface structures, including P1 adhesin and the internal core structure. The core structure can be divided into three parts, the terminal button, paired plates, and bowl complex, aligned in that order from the front end of the protrusion. To elucidate the gliding mechanism, we focused on MPN387, a component protein of the bowl complex which is essential for gliding but dispensable for cytadherence. The predicted amino acid sequence showed that the protein features a coiled-coil region spanning residue 72 to residue 290 of the total of 358 amino acids in the protein. Recombinant MPN387 proteins were isolated with and without an enhanced yellow fluorescent protein (EYFP) fusion tag and analyzed by gel filtration chromatography, circular dichroism spectroscopy, analytical ultracentrifugation, partial proteolysis, and rotary-shadowing electron microscopy. The results showed that MPN387 is a dumbbell-shaped homodimer that is about 42.7 nm in length and 9.1 nm in diameter and includes a 24.5-nm-long central parallel coiled-coil part. The molecular image was superimposed onto the electron micrograph based on the localizing position mapped by fluorescent protein tagging. A proposed role of this protein in the gliding mechanism is discussed.



Human mycoplasma pneumonia is caused by a pathogenic bacterium, Mycoplasma pneumoniae This tiny, 2-μm-long bacterium is suggested to infect humans by gliding on the surface of the trachea through binding to sialylated oligosaccharides. The mechanism underlying mycoplasma "gliding motility" is not related to any other well-studied motility systems, such as bacterial flagella and eukaryotic motor proteins. Here, we isolated and analyzed the structure of a key protein which is directly involved in the gliding mechanism.
Graduate School of Science, Osaka City University, Osaka, Japan.
Yoshito
Y
Kawakita
Graduate School of Science, Osaka City University, Osaka, Japan Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
Miki
M
Kinoshita
Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
Yukio
Y
Furukawa
Graduate School of Science, Osaka City University, Osaka, Japan.
Isil
I
Tulum
Graduate School of Science, Osaka City University, Osaka, Japan.
Yuhei O
YO
Tahara
Graduate School of Science, Osaka City University, Osaka, Japan.
Eisaku
E
Katayama
Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan Riken Quantitative Biology Center, Suita, Osaka, Japan.
Keiichi
0000-0003-2911-5875
K
Namba
Graduate School of Science, Osaka City University, Osaka, Japan The OCU Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka City University, Osaka, Japan miyata@sci.osaka-cu.ac.jp.
Makoto
0000-0002-7478-7390
M
Miyata
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D009068:Movement; D009177:Mycoplasma pneumoniae / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation
D001426:Bacterial Proteins