6IOQ

The ligand binding domain of Mlp24 with glycine

Summary for 6IOQ

• Entry DOI: 10.2210/pdb6ioq/pdb
• Descriptor: Methyl-accepting chemotaxis protein, GLYCINE, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: chemoreceptor, ligand complex, mcp-like protein, pas-like domain, signaling protein
• Biological source: Vibrio cholerae
• Total number of polymer chains: 1
• Total formula weight: 28722.27

Authors

Takahashi, Y.,Sumita, K.,Nishiyama, S.,Kawagishi, I.,Imada, K. (deposition date: 2018-10-31, release date: 2019-03-06, Last modification date: 2024-03-27)

Primary citation

Takahashi, Y.,Nishiyama, S.I.,Sumita, K.,Kawagishi, I.,Imada, K.
Calcium Ions Modulate Amino Acid Sensing of the Chemoreceptor Mlp24 ofVibrio cholerae.
J. Bacteriol., 201:-, 2019

PubMed Abstract: Bacteria sense environmental chemicals using chemosensor proteins, most of which are present in the cytoplasmic membrane. Canonical chemoreceptors bind their specific ligands in their periplasmic domain, and the ligand binding creates a molecular stimulus that is transmitted into the cytoplasm, leading to various cellular responses, such as chemotaxis and specific gene expression. , the causative agent of cholera, contains about 44 putative sensor proteins, which are homologous to methyl-accepting chemotaxis proteins involved in chemotaxis. Two of them, Mlp24 and Mlp37, have been identified as chemoreceptors that mediate chemotactic responses to various amino acids. Although most of the residues of Mlp37 involved in ligand binding are conserved in Mlp24, these chemoreceptors bind the same ligands with different affinities. Moreover, they have distinct cellular roles. Here we determined a series of ligand complex structures of the periplasmic domains of Mlp24 (Mlp24p). The structures revealed that Ca binds to the loop that forms the upper wall of the ligand-binding pocket. Ca does not bind to the corresponding loop of Mlp37, implying that the structural difference of the loop may cause the ligand affinity difference. Isothermal titration calorimetry (ITC) measurements indicated that Ca changes the ligand binding affinity of Mlp24p. Furthermore, Ca affected chemotactic behaviors to various amino acids mediated by Mlp24. Thus, Ca is suggested to serve as a cosignal for the primary signal mediated by Mlp24p, and fine-tunes its chemotactic behavior depending on the Ca concentration by modulating the ligand sensitivity of Mlp24. Mlp24 and Mlp37 are homologous chemoreceptors of that bind various amino acids. Although most of the residues involved in ligand interaction are conserved, these chemoreceptors show different affinities for the same ligand and play different cellular roles. A series of ligand complex structures of the periplasmic region of Mlp24 (Mlp24p) and following ITC analysis revealed that Ca binds to the loop of Mlp24p and modulates the ligand binding affinity of Mlp24p. Moreover, Ca changes the chemotactic behaviors mediated by Mlp24. We propose that Ca acts as a cosignal that modulates the affinity of Mlp24 for the primary signal, thereby changing the chemotactic behavior of .

PubMed: 30745373
DOI: 10.1128/JB.00779-18

Experimental method

X-RAY DIFFRACTION (2.143 Å)