The crystal structure of BTLA/HVEM complex is stored under ID 2AW2 in the Protein Data Bank . The structure indicates that only the first CRD1 part of human HVEM interacts with BTLA. The domain contains four short β-strands, that are connected by three disulfide bonds, formed between cysteine residues 4–15, 16–29 and 19–37. The fragment of the CRD1 domain of HVEM comprising residues 23–39 forms a β-hairpin structure and the 35–39 fragment builds an anti-parallel inter-molecular β-sheet with G° strand of BTLA in the center of the interaction interface . Moreover, the HVEM(23–39) fragment comprises two hot-spots of the BTLA/HVEM interaction: Tyr23 and Val36. We sought to determine whether the HVEM(23–39) fragment could bind BTLA. We therefore performed the molecular dynamics simulation of the BTLA structure and the HVEM(23–39) fragment (Ac-YRVKEACGELTGTVCEP-NH2). The simulation starting point was a native-like conformation of HVEM fragment, bound to BTLA as in the BTLA/HVEM complex structure (Fig 1). The complex was stable during the 10ns long molecular dynamics simulation. The averaged RMSD calculated for the backbone atoms of the superimposed over carbons alpha structures was 1.2Å. Besides, the hydrogen bonds interactions observed in the starting structure were almost all preserved during the simulation (S1 Table). This computational results suggests that the HVEM(23–39) may stably interact with BTLA.