ABSTRACT
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.
Subject(s)
Catalytic Domain/physiology , Cyclic GMP-Dependent Protein Kinases/metabolism , Molecular Probes/metabolism , Peptides/metabolism , Cyclic GMP-Dependent Protein Kinases/chemistry , Protein Structure, TertiaryABSTRACT
This paper describes conformational studies of proline-templated amino acids (PTAAs) based on the 3-azabicyclo[3.1.0]hexane system as well as conformational studies on short peptides composed of these PTAAs. NOE data, coupling constants, and molecular modeling are consistent with a flattened boat conformation for monomeric and oligomeric residues based on this bicyclic system. NMR studies on dimeric and trimeric oligomers are consistent with a populated poly-L-proline type II conformation in CDCl3 and D2O. Solution studies and molecular modeling predicts phi approximately -70 degrees, psi approximately 131 degrees, chi 1 approximately -57 degrees, and chi 2 approximately -158 degrees for oligomeric residues.
Subject(s)
Bridged Bicyclo Compounds, Heterocyclic/chemistry , Bridged Bicyclo Compounds, Heterocyclic/chemical synthesis , Peptides/chemistry , Proline , Dimerization , Indicators and Reagents , Molecular Conformation , Molecular Structure , Protein Conformation , Structure-Activity RelationshipABSTRACT
[reaction: see text] Solid-phase guanidinylation of proline-templated amino acids is studied as a diversification strategy of poly-L-proline type II scaffolds.
Subject(s)
Guanidine/chemistry , Molecular Mimicry , Peptides/chemistry , Molecular StructureABSTRACT
Eighteen analogues of the nonintercalative DNA topoisomerase II (topo II)-active epipodophyllotoxin-ellipticine hybrid, azatoxin, were synthesized and evaluated for their ability to induce topo II-mediated DNA strand breaks in vitro. In general, the SAR profile of the azatoxins showed more homology with that of the epipodophyllotoxins than with the ellipticines. Of the compounds studied, only fluoro substitution at the 8-, 9, and 10-positions of azatoxins enhanced activity, with 9-fluoroazatoxin being the most active compound in this series.
Subject(s)
DNA Topoisomerases, Type II/metabolism , DNA/metabolism , Indoles/pharmacology , Hydrolysis , Indoles/chemistry , Magnetic Resonance Spectroscopy , Spectrometry, Mass, Fast Atom Bombardment , Structure-Activity RelationshipABSTRACT
A series of novel C11-substituted derivatives of azaelliptitoxin (azatoxin) have been synthesized and tested for their inhibitory activity against human DNA topoisomerase II. Incorporation of a C11 polyamine or amine resulted in an increase in the intercalation properties of the drug and a decrease of topoisomerase II activity. The structure-activity relationship (SAR) profile of the nonintercalating C11 anilino azatoxin class follows the SAR of the (anilino)acridine family. 11-(4-Cyanoanilino)azatoxin (14) was found to be the most active analog in this series, exhibiting approximately 10-fold higher activity than azatoxin 12 and etoposide.
