A Potent Cyclic Peptide Targeting SPSB2 Protein as a Potential Antiinfective Agent

摘要

The protein SPSB2 mediates proteosomal degradation of inducible nitric oxide synthase (iNOS). Inhibitors of SPSB2?iNOS interaction may prolong the lifetime of iNOS and thereby enhance the killing of persistent pathogens. We have designed a cyclic peptide, Ac-c[CVDINNNC]-NH_2, containing the key sequence motif mediating the SPSB2?iNOS interaction, which binds to the iNOS binding site on SPSB2 with a K_d of 4.4 nM, as shown by SPR, [~1H,~(15)N]-HSQC, and ~(19)F NMR. An in vitro assay on macrophage cell lysates showed complete inhibition of SPSB2?iNOS interactions by the cyclic peptide. Furthermore, its solution structure closely matched (backbone rmsd 1.21 ?) that of the SPSB2-bound linear DINNN peptide. The designed peptide was resistant to degradation by the proteases pepsin, trypsin, and chymotrypsin and stable in human plasma. This cyclic peptide exemplifies potentially a new class of anti-infective agents that acts on the host innate response, thereby avoiding the development of pathogen resistance.