Open AccessNovel Antibacterial Activity of β2-Microglobulin in Human Amniotic Fluid
Author(s) -
JinYoung Kim,
Seong-Cheol Park,
Jong-Kook Lee,
Sang Joon Choi,
Kyung–Soo Hahm,
Yoonkyung Park
Publication year - 2012
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0047642
Subject(s) - antibacterial activity , chemistry , peptide sequence , biochemistry , molecular mass , microbiology and biotechnology , biology , bacteria , enzyme , gene , genetics
An antibacterial protein (about 12 kDa) was isolated from human amniotic fluid through dialysis, ultrafiltration and C18 reversed-phase HPLC steps. Automated Edman degradation showed that the N-terminal sequence of the antibacterial protein was NH 2 -Ile-Gln-Arg-Thr-Pro-Lys-Ile-Gln-Val-Tyr-Ser-Arg-His-Pro-Ala-Glu-Asn-Gly-. The N-terminal sequence of the antibacterial protein was found to be identical to that of β 2 -microglobulin, a component of MHC class I molecules, which are present on all nucleated cells. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) revealed that the molecular mass of the antibacterial protein was 11,631 Da. This antibacterial protein, β 2 M, possessed potent antibacterial activity against pathogenic bacteria. Specially, antibacterial activity was observed in potassium buffer, and potassium ion was found to be critical for the antibacterial activity. Interestingly, the antibacterial action of β 2 M was associated with dissipation of the transmembrane potential, but the protein did not cause damage to the membrane that would result in SYTOX green uptake. In addition, stimulation of WISH amniotic epithelial cells with the bacterial endotoxin lipopolysaccharide (LPS) induced dose-dependent upregulation of β 2 M mRNA expression. These results suggest that β 2 M contributes to a self-defense response when amniotic cells are exposed to pathogens.