The cDNA of the neutrophil antibiotic Bac5 predicts a pro-sequence homologous to a cysteine proteinase inhibitor that is common to other neutrophil antibiotics.
Bac5 is a 5-kDa proline- and arginine-rich antibiotic, stored as inactive precursor (proBac5) in the large granules of bovine neutrophils. A full-length cDNA encoding the precursor form of Bac5 has been cloned. The encoded protein (pre-proBac5) has a calculated mass of 20,031 Da and a pI of 9.21. This comprises a putative signal peptide of 29 amino acid residues and a 101-residue pro-sequence that precede the mature antibiotic. The pro-sequence is acidic and may neutralize the highly cationic Bac5, thus accounting for the inactivation of the antibiotic activity observed in in vitro experiments. The structure of mature Bac5 agrees closely with the amino acid sequence previously determined, with an additional tripeptide tail predicting carboxyl-terminal amidation. A valyl residue is deduced at the cleavage site for the proteolytic maturation of proBac5, consistent with a previous observation showing elastase as the enzyme involved in this processing step. The region upstream of Bac5 reveals high identity to corresponding regions of two neutrophil antimicrobial polypeptides, CAP18 from rabbit and bovine indolicidin. The COOH-terminal sequences of these antibiotics are completely unrelated. The proregion also exhibits remarkable similarity to pig cathelin, an inhibitor of cathepsin L, indicating a common evolutionary origin.
Zanetti
M
M
Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, Università di Trieste, Italy.
Del Sal
G
G
Storici
P
P
Schneider
C
C
Romeo
D
D
D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D001483:Base Sequence; D001853:Bone Marrow / Q000502:physiology; D002417:Cattle; D003001:Cloning, Molecular; D015853:Cysteine Proteinase Inhibitors / Q000235:genetics*; D004247:DNA / Q000235:genetics*; D047091:Eosinophil Granule Proteins; D015723:Gene Library; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000502:physiology*; D009838:Oligodeoxyribonucleotides; D010455:Peptides / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011498:Protein Precursors / Q000235:genetics*; D011506:Proteins / Q000235:genetics*; D011817:Rabbits; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; C078861:CATHL2 protein, Bos taurus; D015853:Cysteine Proteinase Inhibitors; D047091:Eosinophil Granule Proteins; D009838:Oligodeoxyribonucleotides; D010455:Peptides; D011498:Protein Precursors; D011506:Proteins; C073143:indolicidin; D004247:DNA