ABSTRACT
Removal of the fucose residue from the oligosaccharides attached to Asn297 of human immunoglobulin G1 (IgG1) results in a significant enhancement of antibody-dependent cellular cytotoxicity (ADCC) via improved IgG1 binding to Fcgamma receptor IIIa. To provide structural insight into the mechanisms of affinity enhancement, we determined the crystal structure of the nonfucosylated Fc fragment and compared it with that of fucosylated Fc. The overall conformations of the fucosylated and nonfucosylated Fc fragments were similar except for hydration mode around Tyr296. Stable-isotope-assisted NMR analyses confirmed the similarity of the overall structures between fucosylated and nonfucosylated Fc fragments in solution. These data suggest that the glycoform-dependent ADCC enhancement is attributed to a subtle conformational alteration in a limited region of IgG1-Fc. Furthermore, the electron density maps revealed that the traces between Asp280 and Asn297 of our fucosylated and nonfucosylated Fc crystals were both different from that in previously reported isomorphous Fc crystals.
Subject(s)
Amino Acids/chemistry , Fucose/chemistry , Immunoglobulin Fc Fragments/chemistry , Immunoglobulin G/chemistry , Models, Molecular , Animals , CHO Cells , Carbohydrate Sequence , Cricetinae , Cricetulus , Crystallography, X-Ray , Glycosylation , Humans , Magnetic Resonance Spectroscopy , Molecular Sequence Data , Protein Conformation , SolutionsABSTRACT
A novel piperidine series of farnesyltransferase (FTase) inhibitors is described. Systematic medicinal chemistry studies starting with the lead compound, discovered from a 5-nitropiperidin-2-one combinatorial library, resulted in a potent series of novel FTase inhibitors. We found that all of four substituents of the piperidine core played an important role for FTase inhibition. A 10-fold increase in potency was observed by changing the piperidine-2-one core to the corresponding piperidine core. This class of compounds was found to inhibit farnesyltransferase in a Ras competitive manner. Optical resolution of several potent inhibitors revealed that the (+)-enantiomers showed potent farnesyltransferase inhibition. (+)-8 inhibited FTase with an IC(50) of 1.9 nM.
Subject(s)
Alkyl and Aryl Transferases/antagonists & inhibitors , Enzyme Inhibitors/chemical synthesis , Piperidines/chemical synthesis , Alkyl and Aryl Transferases/chemistry , Animals , Cattle , Chromatography, High Pressure Liquid , Combinatorial Chemistry Techniques , Crystallography, X-Ray , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Farnesyltranstransferase , Humans , Kinetics , Magnetic Resonance Spectroscopy , Piperidines/chemistry , Piperidines/pharmacology , Stereoisomerism , Structure-Activity Relationship , Tumor Cells, Cultured , ras Proteins/metabolismABSTRACT
[structure: see text] UCS1025A and B, novel pentacyclic polyketides with an unprecedented furopyrrolizidine skeleton, were isolated from the fungus Acremonium sp. KY4917. The structures and stereochemistry were elucidated by a combination of two-dimensional NMR and X-ray crystallographic analysis. UCS1025A showed unique chemical equilibria involving three tautomeric isomers and exhibited antimicrobial activity and antiproliferative activity against human tumor cell lines.
