Bacterial methyl-accepting chemotaxis proteins (MCP) are the membrane bound receptors responsible for regulating swimming behavior in response to the extracellular chemicals ques. MCP forms a homodimer consisting of periplasmic ligand binding domain, a transmembrane domain, and a cytoplasmic signaling domain. Although their structural architecture and signaling mechanism are well conserved in many bacterial species, detailed structural information of the signaling domain has not been elucidated yet, especially, in the membrane lipid bilayer. In this study, Tsr, a serine chemoreceptor in Escherichia coli, has been used for the structural study of MCP in the lipid bilayer. The recombinant Tsr was overexpressed in E. coli and purified followed by the reconstitution into nanodiscs for providing the lipid bilayer environment. Structural characteristics of Tsr in nanodiscs were first investigated by the transmission electron microscopy (TEM) with negative staining followed by cryo-EM. EM studies revealed that Tsr was successfully reconstituted into nanodisc as one to three TSR dimers were identified in one nanodisc. However, while nanodiscs are well elucidated with strong intensity, Tsr was seen as thin tails embedded in the nanodics. Furthermore, cytoplasmic helical tails below HAMP domain showed high flexibility by displaying various conformation in the micrograph, which resulted in disappearance of the most of tail part during 2D classification and averaging steps. These results suggest that Tsr form a strong dimer with flexible conformation in the cytoplasmic signaling domain. However, trimer of dimer is not stable in the lipid bilayer environment although previous studies suggested that dimer forms trimer via interaction among cytoplasmic domains. Further cryoEM studies of Tsr in complex with other signaling mediators such as CheA ad CheW will elucidate the detailed protein interactions and their signaling mechanism.