Abstract: In this study, the tail fiber gene orf38 of Salmonella Podoviridae LPST144 was sequenced and expressed and the product (gp38) was purified, whose specific receptor binding activity was successfully verified, yielding a potential probe for Salmonella detection. Bioinformatics was used to analyze the amino acid sequence, physicochemical properties, genetic evolution relationship and C-terminal secondary structures of LPST144 tail fiber gp38. Results showed that the tail fiber gp38 contained 646 amino acid residues, and two conserved regions with high similarity to T7 existed at its N-terminal. However, the C-terminal sequence was extremely different, and there were large numbers of β-sheet structures similar to the C-terminal secondary structures of T7 tail fiber. gp38 had many features of phage receptor binding proteins such as modular properties, low sequence similarity and β-sheet-rich C-terminal. The ability of the recombinant protein to specifically bind to the host Salmonella typhimurium (ATCC13311) was detected by whole bacterial cell coating ELISA. Results showed that the absorbance value of the experimental group was 0.94 ± 0.02, as compared to 0.17 ± 0.01 for the negative control, indicating strong binding ability to the host cells. The recombinant gp38 could also be combined with six other serotypes of Salmonella tested. When Escherichia coli (T10), Salmonella outer membrane protein, Staphylococcus aureus (6538) and PBS buffer were used instead of the host cells, the absorbance values were 0.58 ± 0.03, 0.56 ± 0.01, 0.59 ± 0.03 and 0.53 ± 0.005, respectively. The observed significant difference between the experimental and control groups indicated that the tail fiber gp38 has the ability to specifically bind to the host S. typhimurium (ATCC13311) and the other serotypes of Salmonella. This study can lay an experimental foundation for the development of Salmonella detection methods using phage receptor binding proteins as a molecular probe.

Key words: Salmonella typhimurium; phage tail fiber; sequence analysis; expression and purification; specific binding ability