Bacteria express beta-lactamase to counteract the bactericidal effects of beta-lactam antibiotics, which are the most widely employed antibacterial drugs. In gram-negative bacteria, the expression of beta-lactamase is generally regulated in response to the neuropeptide that is generated from the peptidoglycan of the cell wall during beta-lactam antibiotic challenge. The direct regulation of beta-lactamase expression by beta-lactams was recently reported in Vibrio parahaemolyticus, and this regulation is mediated by a two-component regulatory system that consists of the histidine kinase VbrK and the response regulator VbrR. VbrK directly recognizes beta-lactam antibiotics using the periplasmic sensor domain (VbrK(SD)), a PF11884 Pfam family member, and it delivers the beta-lactam signal to VbrR to induce the transcription of the beta-lactamase gene. To determine the structural features of VbrK(SD) as the prototype of the PF11884 family and provide insights into the beta-lactam antibiotic-binding mode of VbrK(SD), we determined the crystal structure of VbrK(SD) at 1.65 angstrom resolution. VbrK(SD) folds into a unique curved rod-like structure that has not been previously reported in other families. VbrK(SD) consists of two domains (D1 and D2). The D1 domain contains two helix-decorated beta-sheets, and the D2 domain adopts a helix-rich structure. VbrK(SD) features two terminal disulfide bonds, which would be the canonical property of the PF11884 family. In the VbrK(SD) structure, the L82 residue, which was previously shown to play a key role in beta-lactam antibiotic recognition, forms a pocket along with its neighboring hydrophobic or positively charged residues. (C) 2020 Elsevier Inc. All rights reserved.