In the synthesis domain analysis of lipopolysaccharide, we found that ORF7a had the BPI1 domain (CELYHYQECVR, 15-25). BPI1 domain (Interpro entry: IPR017942, SMART: SM00328) represents the N-terminal domain found in several lipid-binding serum glycoproteins. It includes bactericidal permeability-increasing protein (BPI), lipopolysaccharide-binding protein (LBP). BPI can bind to and neutralize lipopolysaccharides in the outer membrane . Lipopolysaccharide binding protein (LBP) is an endotoxin binding protein closely related to BPI and acts synergistically to promote the host's comprehensive response to invasion 123 . ORF7a (residues 14-96) without the N-terminal signal peptide and the transmembrane region still has the BPI /LBP domain and two ATP binding sites. The BPI1/LBP domain is at the N-terminus of the extracellular ORF7a and is also at the first β-sandwich fold of the Ig-like fold of the extracellular domain (Figure .A). ORF7a has two ATP binding sites, "HYQEC" and "TYEGNS", the former is in the N-terminal BPI1/LBP domain, and the latter is behind the relative direction of the BPI/LBP domain. Interestingly, the ABC transporter domain of ORF7a includes the N-terminal signal region and the transmembrane region. The BPI1 domain of ORF7a is also in the vital region of ABC transport and lipopolysaccharide synthesis domain and is also the lipopolysaccharide-binding region. So the BPI1 domain of extracellular ORF7a is also a lipopolysaccharide-binding domain. It indicates that the splicing of the N-terminal signal peptide and the transmembrane region may trigger ORF7a to lose its ABC transport function and release itself outside the infected cell.