Research presentations
Number of the published data : 8
No. Assortment Title Conference Date URL Description
1 Oral presentation(general)
Structure and function of bacterial signal transducing sensor complexes
The 86th annual meeting of Japanese Society for Bacteriology, International Symposium 2 "Bacterial nanomachines: substrate targeting and translocation"
2013/03/18

In the chemotaxis of Escherichia coli, all of the relevant protein components have been identified and characterized extensively in terms of biochemistry and three-dimensional structures. Thus we can ask the nature of the system at the molecular level. It should be noted that these proteins are not randomly distributed in a cell: the chemoreceptors (MCPs), the histidine kinase CheA and the adaptor CheW form a huge cluster that localizes to a cell pole. Other signaling components co-localize with the MCP-CheW-CheA cluster, resulting in a large sensor/singlaing complex or a signalosome. Clustering of the signaling proteins has been implicated in signal amplification and adaptation. Genome sequencing revealed that some bacterial species, including Vibrio cholerae, are equipped with multiple sets of chemotaxis-like signaling systems. Clustering of the signaling proteins therefore may support coherent signaling by avoiding crosstalk. In this talk, we will discuss on the molecular architecture, biogenesis and physiological significance of the sensor complexes in E. coli and V. cholerae.
2 Oral presentation(general)
増殖停滞期における細菌の環境応答
第85回日本細菌学会総会
2012/03/28


3 Oral presentation(general)
大腸菌走化性のミッシングリンク:忌避応答のメカニズムを探る
2011年度遺伝研研究会「単細胞生物における細胞構築と増殖制御の研究」
2012/03/21


4 Oral presentation(general)
Interigent sensing in organisms: toward understanding how bacterial poymodal sensors work
ナノ・バイオ ICTシンポジウム ~バイオに学ぶ未来ICT型センシングテクノロジー~
2012/02/15

生物にとって「センシング」は普遍的かつ重要な機能である.どの細胞も環境変化を的確にモニターし,適切に応答しなければ生きていけない.それは体長わずか数µmの小さな細菌たちでも同様で,一見単純に見えるが,地球上のさまざまな環境中で生きていくために,巧妙なセンシングシステムを備えている.例えば,大腸菌は,細胞内外の環境変化を感知する.ほとんどの場合,細胞外からの刺激を認識するセンサーは,細胞膜に存在するタンパク質(受容体)であり,その後の情報プロセシングも,おもにタンパク質が担う.多くの場合,最終的な出力は遺伝子の発現制御であり,比較的時間のかかる応答である.それに対し,遺伝子発現制御を伴わない瞬時の応答も必要である.その代表例が走化性である.走化性とは,"好ましい"環境を感知してその場所に集まる能力であり,いわば原始的な「感覚系」である.その情報の入力から出力までの全ての因子が同定されており,精力的に研究されている.この系では,微細な入力を増幅できること,一定の刺激が持続すると応答が減衰すること(適応)など,感覚系一般に見られる特徴を備えている.走化性受容体は,複数の化学物質のほか,温度やpHも認識する多機能センサーとして注目される.また,この受容体は,他のシグナル伝達タンパク質とともに,細胞の極で巨大クラスターを形成して機能する.本講演では,走化性受容体の構造・機能・局在を中心に,生物のもつ巧妙なセンシング機能とそれを実現するしくみについての現在の知見を紹介したい.
5 Poster presentation
Mechanisms of amino acid ligand recognition by bacterial chemoreceptors
Gordon Research Conference on Sensory Transduction in Microorganisms
2012/01


6 Oral presentation(general)
細菌環境応答の分子メカニズムを探る
第10回微生物研究会
2011/11


7 Oral presentation(general)
Mechanisms of ligand recognition by the amino acid chemoreceptors of Vibrio cholerae
日本生物物理学会 第49回年会
2011/09

Vibrio cholerae, an etiological agent of cholera, shows chemotaxis, which is implicated in pathogenicity as well as survival in various environments. A classical biotype strain of V. cholerae O395N1 appear to possess 44 chemoreceptor homologs, which we name methyl-accepting chemotaxis protein-like proteins (MLPs). Among them, Mlp24 and Mlp37, which are highly homologous to each other, mediate attractant responses to serine and other amino acids. The periplasmic domain of Mlp37 is mainly composed of two tandem-linked homologous domains (named PAS-like domains) with two putative binding pockets. Isothermal calorimetric (ITC) measurements using purified periplasmic fragments of Mlp24 and Mlp37 strongly suggest direct binding of various amino acids with few exception. To understand the ligand-recognition mechanism, we mutated residues of putative binding pockets of Mlp24 and Mlp37. The results suggest that pocket I, but not pocket II, is involved in amino acid recognition. We also found that Mlp2 and Mlp3, each with only one periplasmic PAS-like domain, mediate attractant responses to serine and other amino acids. Roles of these PAS-like domains will be discussed.
8 Oral presentation(general)
Mechanisms of ligand recognition by bacterial chemoreceptors
Union of Microbiological Societies 2011 Congress (IUMS 2011)
2011/09

Flagellated bacteria are attracted by some nutrients such as amino acids and sugars and repelled by some harmful substances such as metal ions and hydrophobic compounds. The sensor for such attractants and repellents are methyl-accepting chemotaxis proteins (MCPs), also known as chemoreceptors, that in most cases localize to the cytoplasmic membrane. Escherichia coli has closely related amino acid chemoreceptors with distinct ligand specificity: Tar for L-aspartate and Tsr for L-serine. We recently found that chemoreceptors of Vibrio cholerae, which we name Mlp24 and Mlp37, mediate attractant responses to overlapped but distinct sets of amino acids. Mlp24 is of special interest since it is also implicated in pathogenicity and Mlp37 is highly homologous to Mlp24, but their periplasmic sensor domains are not related to those of Tar and Tsr. The three-dimensional structures of the sensor domains of these two distinct families of amino acid chemoreceptors are solved to date. MCPs are unique in that they can sense multiple stimuli. In particular, the E. coli chemoreceptors also mediate repellent responses: Tar for Ni2+ and Co2+ and Tsr for luecine and indole. However, the mechanisms underling repellent sensing have been largely unknown. This talk will focus on our recent studies on ligand recognition mechanisms of these two types of chemoreceptors.