Poster Presentation The 43rd Lorne Conference on Protein Structure and Function 2018

Structural and biochemical characterisation of SARM Including mutagenesis analysis of tandem SAM domains and investigating auto-regulation of ARM domain (#132)

Xing Gui 1 , Weixi Gu 1 , Shane Horsefield 1 , Bostjan Kobe 1
  1. School of Chemistry and Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia

Sterile α and armadillo-motif-containing protein (SARM) plays a dominant role in promoting axon degeneration, which is a process that eliminating damaged or unwanted neurons as a response to injury and during development. SARM was originally found to inhibit TLR siganalling and leading to cell death. The protein is highly conserved from worm to human which is consisted of an N-terminal armadillo repeat motif (ARM), two central tandem sterile α-motif (SAM) domains and a C-terminal Toll/interleukin-1 receptor (TIR) domain. Previous research had shown that tandem SAM domains were responsible for multimerisation which brought multiple TIR to closed proximity and activated SARM, ARM domain played an auto-inhibitory role in SARM, but the mechanism and how SARM is activated is unknown. In this project, we had found that the interfaces of SAM-SAM association are different from different species in SARM orthologs. In terms of ARM domain characterisation, we have solved the problem of insoluble protein of ARM domain by successfully purifying an ARM protein of C. elegans SARM, however, large amounts of contaminating protein were present. We also found that ARM domain protein may exist in two oligomeric states. In order to get much purer ARM protein, we tried several alternative pH values of buffers, however, it did not seem to work. In the future, when purer ARM protein can be obtained, crystallisation and X-ray diffraction can be applied for detailed structural studies for ARM domain to eventually solve the regulatory mechanism of ARM domain in SARM, hopefully SARM could become a potential therapeutic target for pathological axon loss.