Assuntos
Linhagem da Célula , Resistencia a Medicamentos Antineoplásicos/genética , Histona-Lisina N-Metiltransferase/genética , Proteínas de Homeodomínio/genética , Proteína de Leucina Linfoide-Mieloide/genética , Recidiva Local de Neoplasia/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Adolescente , Adulto , Criança , Pré-Escolar , Intervalo Livre de Doença , Feminino , Rearranjo Gênico , Humanos , Masculino , Recidiva Local de Neoplasia/mortalidade , Leucemia-Linfoma Linfoblástico de Células T Precursoras/mortalidade , Prognóstico , Estudos RetrospectivosRESUMO
Based on the X-ray crystal structure of cAMP-dependent protein kinase (PKA) with the endogenous inhibitor PKI and the X-ray crystal structure of cyclin-dependent kinase 2 (CDK2) with a substrate peptide, a proposal is put forth that some protein kinases bind peptide substrates in their active sites in the poly-L-proline type II (PPII) conformation. In this work, PPII peptide mimics are evaluated as pseudosubstrate inhibitors of cGMP-dependent protein kinase (PKG) to explore if PKG also binds peptide substrates in the PPII conformation. Inhibition data of our PPII mimetics provide evidence that the P-1, P-2, and P-3 residues of substrate peptides bind in the PPII conformation (phi approximately -75 degrees, psi approximately 145 degrees). In addition, the inhibition data also suggest that the P-1, P-2, and P-3 residues in substrate peptides bind with a gauche(-) chi1 angle.
Assuntos
Domínio Catalítico/fisiologia , Proteínas Quinases Dependentes de GMP Cíclico/metabolismo , Sondas Moleculares/metabolismo , Peptídeos/metabolismo , Proteínas Quinases Dependentes de GMP Cíclico/química , Estrutura Terciária de ProteínaRESUMO
Arrays of octameric peptide libraries on cellulose paper were screened by using (32)P-autophosphorylated cGMP-dependent protein kinase Ialpha (cGPK) to identify peptide sequences with high binding affinity for cGPK. Iterative deconvolution of every amino acid position in the peptides identified the sequence LRK(5)H (W45) as having the highest binding affinity. Binding of W45 to cGPK resulted in selective inhibition of the kinase with K(i) values of 0.8 microM and 560 microM for cGPK and cAMP-dependent protein kinase (cAPK), respectively. Fusion of W45 to membrane translocation signals from HIV-1 tat protein (YGRKKRRQRRRPP-LRK(5)H, DT-2) or Drosophila Antennapedia homeo-domain (RQIKIWFQNRRMKWKK-LRK(5)H, DT-3) proved to be an efficient method for intracellular delivery of these highly charged peptides. Rapid translocation of the peptides into intact cerebral arteries was demonstrated by using fluorescein-labeled DT-2 and DT-3. The inhibitory potency of the fusion peptides was even greater than that for W45, with K(i) values of 12.5 nM and 25 nM for DT-2 and DT-3, respectively. Both peptides were still poor inhibitors of cAPK. Selective inhibition of cGPK by DT-2 or DT-3 in the presence of cAPK was demonstrated in vitro. In pressurized cerebral arteries, DT-2 and DT-3 substantially decreased NO-induced dilation. This study provides functional characterization of a class of selective cGPK inhibitor peptides in vascular smooth muscle and reveals a central role for cGPK in the modulation of vascular contractility.
