Eligible Student Poster 49th Lorne Conference on Protein Structure and Function 2024

Understanding the role of a clostridial sporulation protein in antibiotic resistance (#351)

Clara E Bate 1 2 , Daniel E Williams 1 2 , Chathura D Suraweera 1 2 3 , Chaille T Webb 1 2 , Yogitha N Srikhanta 1 2 , Dena Lyras 1 2 , Sheena McGowan 1 2
  1. Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, VIC, Australia
  2. Centre to Impact AMR, Monash University, Melbourne, VIC, Australia
  3. Genome Sciences and Cancer Division, The John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia

Clostridioides difficile, a spore forming bacterium, is a leading cause of nosocomial infections. C. difficile infections can cause mild symptoms such as diarrhoea, through to more severe disease symptoms, including inflammation and enlargement of the colon. Spores are crucial mediators of C. difficile infection initiation, dissemination, and re-infection, due to their resistance to antimicrobial treatment and disinfection. However, current therapeutics do not directly target sporulation and have no effect on spore formation. Our team has shown that cephamycins, a beta-lactam type antibiotic, can inhibit sporulation by targeting the sporulation specific penicillin binding protein CdSpoVD1. SpoVD proteins are highly conserved among spore forming bacteria and play an essential role during sporulation in C. difficile1. However, our research has identified that sporulation is not inhibited by cephamycins in strains that acquire an additional sporulation specific protein, CdSpoCR. To understand how CdSpoCR facilitates resistance to cephamycins, recombinant CdSpoCR was produced and assessed for its affinity to a panel of clinical antibiotics and the crystal structure solved. Our research shows that CdSpoCR is unable to bind or has low affinity for many clinically relevant beta-lactam antibiotics in comparison to the conserved cephamycin sensitive CdSpoVD. To further understand this observed low affinity, we solved the X-ray crystal structure of CdSpoCR to 2.9 Å and assessed the architecture of the active site. Comparison of the structure of CdSpoVD and CdSpoCR active site shows significant differences in active site access, architecture and electrostatic nature. Here we present the structure of CdSpoCR and discuss the basis of low affinity for beta-lactams.