Secondary Structural Transformation of Bovine Lactoferricin Affects Its Antibacterial Activity
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Secondary Structural Transformation of Bovine Lactoferricin Affects Its Antibacterial Activity Jie Pei 1,2
&
Lin Xiong 1,2 & Pengjia Bao 1,2 & Min Chu 1,2 & Ping Yan 1,2 & Xian Guo 1,2
Accepted: 1 November 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Lactoferricin (Lfcin) is a potent antibacterial peptide derived from lactoferrin by pepsin hydrolysis. It was hypothesized that structural transformation of Lfcin could affect its antibacterial function through forming and breaking of intramolecular disulfide bond. To prove this hypothesis, bovine Lfcin (bLfcin) and its two derivatives, bLfcin with a disulfide bond (bLfcin DB) and bLfcin with a mutation C36G (bLfcin C36G), were synthesized, purified, and identified. The circular dichroism (CD) spectra of the peptides were detected in solutions with different ionic and hydrophobic strength. Then, the secondary structure contents of the peptides were calculated on the basis of the CD spectra. The antibacterial activity of the peptides against Escherichia coli ATCC 25922, Salmonella typhimurium ATCC 14028, Shigella flexneri ATCC 12022, and Staphylococcus aureus ATCC 25923 was evaluated. The results showed that bLfcin and bLfcin C36G had similar percentages of secondary structure in water, while bLfcin and bLfcin DB had similar ratios of secondary structure under less hydrophobic conditions. The synthetic peptides exhibited antibacterial activity against all the tested bacteria, except for S. aureus ATCC 25923. bLfcin demonstrated higher antibacterial activity compared with its derivatives. The results suggested that bLfcin could transform its structure under alterative ionic strengths and hydrophobic conditions, and the transformation of structures was beneficial to enhancing the antibacterial function. Keywords Lactoferricin . Antibacterial activity . E. coli . S. aureus . S. flexneri . S. typhimurium
Introduction The increasing resistance of pathogenic bacteria to conventional antibiotics has become a serious threat to global public health [1], causing limited therapeutic options, minimal effects, extended hospital stay, enhanced treatment costs, and increased mortality [2]. The emergence and spread of antimicrobial resistance are mainly caused by overuse and misuse of antibiotics in human medical treatment [3, 4] and widespread use of antibiotics in agriculture, aquaculture, and livestock production [5, 6]. Some resistant strains, such as E. coli, S. aureus, S. flexneri, and S. typhimurium, can cause a majority of infections acquired during hospitalization. (1) E. coli can be pathogenic both within * Xian Guo [email protected]; [email protected] 1
Lanzhou Institute of Husbandry and Pharmaceutical Sciences, Chinese Academy of Agricultural Sciences, Lanzhou 730050, China
2
Key Lab of Yak Breeding Engineering in Gansu Province, Lanzhou 730050, China
and outside of the gastrointestinal tract [7]. The vast majority of E. coli isolated from clinical extra-intestinal infections are multi-drug resistant [8]. (2) Staphylococcus aureu
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