The mechanism of the cell cycle regulatory peptidyl prolyl isomerase (PPIase), Pin1, was investigated using reduced-amide inhibitors designed to mimic the twisted-amide transition state. Inhibitors, R-pSer-Psi[CH(2)N]-Pro-2-(indol-3-yl)ethylamine, 1 [R = fluorenylmethoxycarbonyl (Fmoc)] and 2 (R = Ac), of Pin1 were synthesized and bioassayed. Inhibitor 1 had an IC(50) value of 6.3 muM, which is 4.5-fold better for Pin1 than our comparable ground-state analogue, a cis-amide alkene isostere-containing inhibitor. The change of Fmoc to Ac in 2 improved aqueous solubility for structural determination and resulted in an IC(50) value of 12 muM. The X-ray structure of the complex of 2 bound to Pin1 was determined to 1.76 A resolution. The structure revealed that the reduced amide adopted a conformation similar to the proposed twisted-amide transition state of Pin1, with a trans-pyrrolidine conformation of the prolyl ring. A similar conformation of substrate would be destabilized relative to the planar amide conformation. Three additional reduced amides, with Thr replacing Ser and l- or d-pipecolate (Pip) replacing Pro, were slightly weaker inhibitors of Pin1.
A reduced-amide inhibitor of Pin1 binds in a conformation resembling a twisted-amide transition state.,Xu GG, Zhang Y, Mercedes-Camacho AY, Etzkorn FA Biochemistry. 2011 Nov 8;50(44):9545-50. Epub 2011 Oct 18. PMID:21980916
From MEDLINEÂ®/PubMedÂ®, a database of the U.S. National Library of Medicine.
↑ Xu GG, Zhang Y, Mercedes-Camacho AY, Etzkorn FA. A reduced-amide inhibitor of Pin1 binds in a conformation resembling a twisted-amide transition state. Biochemistry. 2011 Nov 8;50(44):9545-50. Epub 2011 Oct 18. PMID:21980916 doi:10.1021/bi201055c