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Infect. Immun., Apr 1995, 1291-1297, Vol 63, No. 4
JW Larrick, M Hirata, RF Balint, J Lee, J Zhong and SC Wright
CAP18 (18-kDa cationic antimicrobial protein) is a protein originally
identified and purified from rabbit leukocytes on the basis of its capacity
to bind and inhibit various activities of lipopolysaccharide (LPS). Here we
report the cloning of human CAP18 and characterize the anti-LPS activity of
the C-terminal fragment. Oligonucleotide probes designed from the rabbit
CAP18 cDNA were used to identify human CAP18 from a bone marrow cDNA
library. The cDNA encodes a protein composed of a 30-amino-acid signal
peptide, a 103-amino-acid N-terminal domain of unknown function, and a
C-terminal domain of 37 amino acids homologous to the LPS-binding
antimicrobial domain of rabbit CAP18, designated CAP18(104-140). A human
CAP18-specific antiserum was generated by using CAP18 expressed as a fusion
protein with the maltose-binding protein. Western blots (immunoblots) with
this antiserum showed specific expression of human CAP18 in granulocytes.
Synthetic human CAP18(104- 140) and a more active truncated fragment,
CAP18(104-135), were shown to (i) bind to erythrocytes coated with diverse
strains of LPS, (ii) inhibit LPS-induced release of nitric oxide from
macrophages, (iii) inhibit LPS-induced generation of tissue factor, and
(iv) protect mice from LPS lethality. CAP18(104-140) may have therapeutic
utility for conditions associated with elevated concentrations of LPS.
Copyright © 1995, American Society for Microbiology
Human CAP18: a novel antimicrobial lipopolysaccharide-binding protein
Palo Alto Institute of Molecular Medicine, Mountain View, California 94043.
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