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Purification of the antibacterial fragments of guinea-pig major basic protein
Y Hashimoto1, I Nagaoka, T Yamashita
1Department of Biochemistry, School of Medicine, Juntendo University, Tokyo, Japan.
Abstract:
In this study, we tried to purify the antibacterial fragments of guinea-pig major basic protein (MBP) using Staphylococcus aureus. The antibacterial activity of MBP was not affected by the pyridylethylation, suggesting that the disulfide bonds were not necessary for the antibacterial activity. When pyridylethylated-MBP was digested with alpha-chymotrypsin, the four potent antibacterial fragments (fragment V (Arg105-Tyr119), fragment IX (Thr1-Phe67), fragment X (Ile54-Leu97) and fragment XIII (Arg25-Phe67)) were isolated by reverse-phase high-performance liquid chromatography. Anti-MBP monoclonal antibody, BMK-13 neutralized the antibacterial activity of PE-MBP and fragments IX, X and XIII, but not the activity of fragment V, suggesting that Ile54-Phe67, the common amino-acid sequence of fragments IX, X and XIII, might be involved in the antibacterial activity of MBP. In fact, the synthetic peptide, Ile54-Phe67 exerted the antibacterial activity, and the activity was neutralized with BMK-13. The antibacterial activity of Ile54-Phe67 was lost by the modification with peptidylarginine deiminase which converted arginine residue to citrulline residue, suggesting that the arginine residues may be important for the antibacterial activity.
Insights
Researchers identified key antibacterial fragments of guinea-pig major basic protein (MBP) active against Staphylococcus aureus. The Ile54-Phe67 peptide fragment, containing arginine residues, is crucial for MBP's antibacterial function.
Area of Science:
- Microbiology
- Biochemistry
- Immunology
Background:
- Major basic protein (MBP) from guinea pigs exhibits potent antibacterial properties.
- Understanding the specific domains responsible for MBP's antimicrobial activity is crucial for developing new therapeutic agents.
Purpose of the Study:
- To identify and characterize the antibacterial fragments of guinea-pig MBP.
- To elucidate the role of specific amino acid residues and disulfide bonds in MBP's antibacterial activity.
Main Methods:
- Pyridylethylation of MBP to assess the role of disulfide bonds.
- Digestion of modified MBP with alpha-chymotrypsin.
- Isolation of antibacterial fragments using reverse-phase high-performance liquid chromatography (RP-HPLC).
- Antibacterial assays and neutralization studies using anti-MBP monoclonal antibody (BMK-13).
- Synthesis and testing of specific peptide fragments (Ile54-Phe67).
- Enzymatic modification (peptidylarginine deiminase) to assess the role of arginine residues.
Main Results:
- Pyridylethylation did not abolish MBP's antibacterial activity, indicating disulfide bonds are not essential.
- Four potent antibacterial fragments were isolated, including fragment V (Arg105-Tyr119) and fragment X (Ile54-Leu97).
- The peptide sequence Ile54-Phe67, common to several active fragments, demonstrated antibacterial activity neutralized by BMK-13.
- Modification of arginine residues to citrulline in the Ile54-Phe67 peptide abolished its antibacterial activity.
Conclusions:
- The antibacterial activity of guinea-pig MBP is primarily mediated by specific peptide fragments, notably the Ile54-Phe67 sequence.
- Arginine residues within the Ile54-Phe67 fragment are critical for MBP's antibacterial function.
- These findings provide insights into the mechanism of action of MBP and potential targets for antimicrobial drug development.