Abstact

Novel classes of antibiotics are needed to improve the resilience of the healthcare system to antimicrobial resistance (AMR), including vancomycin resistance. vanA gene cluster is a cause of vancomycin resistance. This gene cluster is transferred and spreads vancomycin resistance from Enterococcus spp. to Staphylococcus aureus. Therefore, novel antibacterial agents are required to combat AMR, including vanA-type vancomycin resistance. Serine hydroxymethyltransferase (SHMT) is a key target of antibacterial agents. However, the specific binding mechanisms of SHMT inhibitors remain unclear. Detailed structural information will contribute to understanding these mechanisms. In this study, we found that (+)-SHIN-2, the first in vivo active inhibitor of human SHMT, is strongly bound to the Enterococcus faecium SHMT (efmSHMT). Comparison of the crystal structures of apo- and (+)-SHIN-2-boud efmSHMT revealed that (+)-SHIN-2 stabilized the active site loop of efmSHMT via hydrogen bonds, which are critical for efmSHMT inhibition. Additionally, (+)-SHIN-2 formed hydrogen bonds with serine, forming the Schiff's base with pyridoxal 5'-phosphate, which is a co-factor of SHMT. Furthermore, (+)-SHIN-2 exerted biostatic effects on vancomycin-susceptible and vanA-type vancomycin-resistant E. faecium in vitro, indicating that SHMT inhibitors do not induce cross-resistance to vanA-type vancomycin. Overall, these findings can aid in the design of novel SHMT inhibitors to combat AMR, including vancomycin resistance.