RESUMO
A novel clone (C6) encoding the precursor of a 79-residue proline/arginine-rich antibacterial peptide prophenin was isolated from a porcine bone marrow cDNA library. Its deduced N-terminal propart shows 84% identity with cathelin. Additionally, two cathelin isoforms were isolated from peripheral porcine blood and their N-termini sequenced. The sequence of one isoform corresponds to the cathelin sequence, whereas that of the other protein is identical to the propeptide of C6 clone. Western blot analysis of total proteins from porcine and human bone marrow using polyclonal antibodies against cathelin revealed the presence of immunochemically related high molecular mass proteins of about 30 kDa in both samples, whereas low molecular mass proteins of approximately 12 kDa, corresponding to isolated cathelin, were not detected in human bone marrow.
Assuntos
Biossíntese Peptídica , Biossíntese de Proteínas , Proteínas/química , Sequência de Aminoácidos , Animais , Western Blotting , Medula Óssea/metabolismo , Clonagem Molecular , DNA Complementar/biossíntese , Humanos , Imunoquímica , Dados de Sequência Molecular , Peptídeos/química , Peptídeos/farmacologia , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/farmacologia , SuínosRESUMO
A new stefin type low-M(r) cysteine proteinase inhibitor (PLCPI) was isolated from pig polymorphonuclear leukocytes as a contaminant of the cathelin sample. The inhibitor consists of 103 amino acids, and its M(r) was calculated to be 11,768. The inhibitor exhibits considerable sequence identity with inhibitors from the stefin family, particularly with human stefin A. The PLCPI is a fast acting inhibitor of papain and cathepsins L and S (k(ass) > or = 1 x 10(6) M-1 x s-1) and forms very tight complexes with these enzymes (Ki < or = 190 pM). The affinity for cathepsins B and H (Ki > or = 125 nM) was lower. These results also show that the inhibitory activity previously ascribed to cathelin was due to the presence of PLCPI.