Isolation and biochemical characterization of LEAP-2, a novel blood peptide expressed in the liver.
The human genome contains numerous genes whose protein products are unknown in terms of structure, interaction partner, expression, and function. To unravel the function of these orphan genes, it is of particular value to isolate native forms of protein and peptide products derived from these genes. From human blood ultrafiltrate, we characterized a novel gene-encoded, cysteine-rich, and cationic peptide that we termed liver-expressed antimicrobial peptide 2 (LEAP-2). We identified several circulating forms of LEAP-2 differing in their amino-terminal length, all containing a core structure with two disulfide bonds formed by cysteine residues in relative 1-3 and 2-4 positions. Molecular cloning of the cDNA showed that LEAP-2 is synthesized as a 77-residue precursor, which is predominantly expressed in the liver and highly conserved among mammals. This makes it a unique peptide that does not exhibit similarity with any known human peptide regarding its primary structure, disulfide motif, and expression. Analysis of the LEAP-2 gene resulted in the identification of an alternative promoter and at least four different splicing variants, with the two dominating transcripts being tissue-specifically expressed. The largest native LEAP-2 form of 40 amino acid residues is generated from the precursor at a putative cleavage site for a furin-like endoprotease. In contrast to smaller LEAP-2 variants, this peptide exhibited dose-dependent antimicrobial activity against selected microbial model organisms. LEAP-2 shares some characteristic properties with classic peptide hormones and it is expected that the isolation of this novel peptide will help to unravel its physiological role.
Krause
Alexander
A
IPF PharmaCeuticals GmbH, Hannover, Germany.
Sillard
Rannar
R
Kleemeier
Burkhard
B
Klüver
Enno
E
Maronde
Erik
E
Conejo-García
José Ramon
JR
Forssmann
Wolf Georg
WG
Schulz-Knappe
Peter
P
Nehls
Michael C
MC
Wattler
Frank
F
Wattler
Sigrid
S
Adermann
Knut
K
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology; D001483:Base Sequence; D001798:Blood Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004220:Disulfides / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D006440:Hemofiltration; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009928:Organ Specificity; D012441:Saccharomyces cerevisiae / Q000187:drug effects; D016415:Sequence Alignment; D021241:Spectrometry, Mass, Electrospray Ionization
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D018076:DNA, Complementary; D004220:Disulfides; C475606:liver-expressed antimicrobial peptide 2, human