Biochemical and biophysical characterisation of the non-methylated state of FrzCD, the cytoplasmic receptor of the Frz pathway

Abstract

The complex lifecycle of Myxococcus xanthus is facilitated by two types of motility, in addition to several other pathways that regulate its lifecycle. The frz pathway modulates the cellular reversal frequency and plays an important role in regulating both the adventurous and social motilities of this bacteria. The foremost enzyme in this frz pathway – FrzCD is a cytoplasmic chemoreceptor. Different post-translational modifications of FrzCD correspond to different states of the receptor and can activate or repress the signalling pathway resulting in modulation of the cellular reversal frequency. In this study, we sought out to characterise one of the states – the unmethylated form of the receptor, using a combination of biophysical approaches to decipher the oligomeric state of the protein. Biochemical means to dissect the protein into its constituent N and C-terminal domains to assign its structure and function, and subsequent biophysical characterisation to assess the quality of the protein sample were carried out. During this process, we discovered that the N-terminal domain of FrzCD binds to DNA, the first instance of a methyl-acepting chemosensory protein (MCP) binding to DNA.