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Antimicrobial actions of calcium binding leucocyte L1 protein, calprotectin
M Steinbakk1, C F Naess-Andresen, E Lingaas
1Department of Microbiology, Ullevaal Hospital, Oslo, Norway.
Abstract:
The calcium binding L1 protein was found to inhibit growth of blood culture isolates of Candida spp and cerebrospinal fluid isolates of Cryptococcus neoformans. Minimum inhibitory concentrations (MIC) were 4-128 mg/l, and concentrations 2-4 times the MIC were fungicidal. Blood culture isolates of Escherichia coli, Klebsiella spp, Staphylococcus aureus, and Staphylococcus epidermidis had MIC values of 64-256 mg/l. Antibacterial activity was strongly influenced by the nature of the culture medium. In view of the biological activity of L1, the name calprotectin is proposed to describe this antimicrobial protein with calcium binding properties.
Insights
The L1 protein, now named calprotectin, inhibits Candida and Cryptococcus fungal growth. It also shows antibacterial activity against E. coli and Staphylococcus species, with effectiveness varying by culture medium.
Area of Science:
- Microbiology
- Biochemistry
- Immunology
Background:
- The L1 protein is a calcium-binding protein with previously unknown biological activities.
- Understanding the antimicrobial spectrum and properties of novel proteins is crucial for developing new therapeutic agents.
Purpose of the Study:
- To investigate the antimicrobial activity of the calcium-binding L1 protein against various microbial pathogens.
- To determine the minimum inhibitory concentrations (MIC) and fungicidal activity of L1.
- To propose a new name for the L1 protein based on its observed properties.
Main Methods:
- Microbiological assays were performed to determine the minimum inhibitory concentrations (MIC) of L1 protein against Candida spp., Cryptococcus neoformans, Escherichia coli, Klebsiella spp., Staphylococcus aureus, and Staphylococcus epidermidis.
- Fungicidal activity was assessed by exposing fungi to concentrations 2-4 times the MIC.
- The influence of culture medium composition on antibacterial activity was evaluated.
Main Results:
- The L1 protein inhibited the growth of Candida spp. and Cryptococcus neoformans with MICs ranging from 4-128 mg/l.
- Concentrations of L1 protein 2-4 times the MIC demonstrated fungicidal effects.
- Antibacterial activity was observed against E. coli, Klebsiella spp., S. aureus, and S. epidermidis, with MICs of 64-256 mg/l, and was significantly influenced by the culture medium.
Conclusions:
- The L1 protein exhibits significant antifungal activity against clinically relevant yeasts and fungi.
- The protein also possesses antibacterial properties, although these are modulated by the growth environment.
- The calcium-binding L1 protein is proposed to be named calprotectin, reflecting its antimicrobial and calcium-binding characteristics.